Stratigraphic formations in the southeastern USA

Neogene deposits of the eastern coast of North America are known for diverse fossil echinoid faunas that peaked in diversity during the Late Pliocene (Osborn et al., Reference Osborn, Portell and Mooi2020). After a sea-level regression in the Early Pliocene (Osborn et al., Reference Osborn, Portell and Mooi2020), the Late Pliocene of the eastern coast of North America was marked by a significant marine transgression recorded by extended synchronous deposits. The beginning of the Late Pliocene is associated with a return of warm tropical to subtropical climates (Mid-Pliocene Warming Event), with average temperatures estimated to be 3.5°C higher than today (Raymo et al., Reference Raymo, Grant, Horowitz and Rau1996; Petuch, Reference Petuch2004). These elevated temperatures and the rise in sea level likely contributed to the diversification of echinoids. Piacenzian deposits of the region contain a very diverse echinoid fauna, exceeded only by the Eocene echinoid fauna in the region (Osborn et al., Reference Osborn, Mooi and Ciampaglio2016).

Pliocene deposits in the southeastern USA

During the period of expansion of warmer seas in the Middle to Late Pliocene, Arbacia diversified throughout the eastern USA. The oldest Arbacia in the region is A. improcera, from the Yorktown Formation that crops out in Virginia and North Carolina (Conrad, Reference Conrad1843a). Arbacia improcera was described from the Yorktown Formation north of Smithfield, Isle of Wight County, Virginia. Kier (Reference Kier1972) called this locality Mogarts Beach while discussing this and other sites’ echinoid faunas in the Yorktown Formation of Virginia. Kier (Reference Kier1972) followed Gibson (Reference Gibson1967) and Hazel (Reference Hazel1971) in attributing these echinoid-rich strata to the Late Miocene. Ward and Blackwelder (Reference Ward and Blackwelder1980) reassigned the lower portion of the Formation to the Upper Miocene Eastover Formation. Based on molluscan faunas, they assigned the Yorktown Formation to the Early Pliocene and described four members: Sunken Meadow, Rushmere, Mogarts Beach, and Moore House, in stratigraphic order. M.R. Campbell (Reference Campbell1995) advised caution about these designations because the Rushmere, Mogarts Beach, and Moore House Members are not pervasive, single-lithology units. Mogarts Beach (now covered by erosion control efforts) is likely the type locality of A. improcera and was referred to the Late Pliocene (Dowsett et al., Reference Dowsett, Robinson, Foley and Herbert2021).

Arbacia improcera (see Kier, Reference Kier1983) and Arbacia cf. A. sloani (see Weaver et al., Reference Weaver, Richard and Chandler2006) were reported from the Yorktown Formation in the PCS Phosphate (Lee Creek) Mine near Aurora in Beaufort County, North Carolina. Specimens were attributed to the Lower Pliocene Sunken Meadow Member (Dowsett et al., Reference Dowsett, Robinson, Foley and Herbert2021), but evidence is insufficient to support this without access to in situ exposures in the quarry’s high walls. Yorktown Formation material was usually float amassed as overburden while quarrying continued in the underlying phosphate-rich strata of the Miocene Pungo River Formation. The type specimen was more likely collected from mixed spoil, and not likely to represent the only known Early Pliocene occurrence of this taxon.

Arbacia improcera occurs in other localities in Virginia (Kier, Reference Kier1972) and south of the type locality to Florida. It is reported in the Upper Pliocene lower Goose Creek Limestone of South Carolina (M.R. Campbell and Campbell, Reference Campbell and Campbell1995; Ciampaglio et al., Reference Ciampaglio, Osborn and Weaver2009), the Upper Pliocene Intracoastal Formation (Ciampaglio and Osborn, Reference Ciampaglio and Osborn2011; Osborn et al., Reference Osborn, Portell and Mooi2020), and the Tamiami Formation of southern Florida (Kier, Reference Kier1963; Osborn et al., Reference Osborn, Portell and Mooi2020). Along with Echinocardium orthonotum (Conrad, Reference Conrad1843b), it is the most widespread Late Pliocene echinoid in the eastern USA.

The most diverse Pliocene echinoid fauna of the Atlantic coast is found within the Goose Creek Limestone (GCLS) in eastern South Carolina (Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019). Tuomey (Reference Tuomey1848) originally described outcrops eventually referred to as Goose Creek Limestone in and around Charleston, South Carolina (M.R. Campbell and Campbell, Reference Campbell and Campbell1995; Tuomey, Reference Tuomey1848). Although Sloan (Reference Sloan1908) coined the name Goose Creek phase for a section of strata along Goose Creek, north of Charleston, it was poorly defined until Weems et al. (Reference Weems, Lemon, McCartan, Bybell and and Sanders1982) formalized the Goose Creek Limestone for Charleston’s Pliocene limestones.

M.R. Campbell and Campbell (Reference Campbell and Campbell1995) subdivided the Goose Creek Limestone Formation into informal lower Goose Creek Limestone (LGCLS) and upper Goose Creek Limestone (UGCLS) members, separated by an unconformity. These included strata formerly referred to as the Duplin Marl in the LGCLS and the Bear Bluff Formation in the UGCLS. These are lithologically identical but differ in the composition of the molluscan fauna (M.R. Campbell and Campbell, Reference Campbell and Campbell1995). Although the LGCLS contains echinoids—Encope macrophora (Ravenel, Reference Ravenel1842) and A. improcera—a much more diverse echinoid fauna is found in the UGCLS (M.R. Campbell and Campbell, Reference Campbell and Campbell1995; Ciampaglio et al., Reference Ciampaglio, Osborn and Weaver2009; Ciampaglio and Osborn, Reference Ciampaglio and Osborn2011; Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019), which contains A. waccamaw and 13 additional species. The presence of E. macrophora and A. improcera in the LGCLS indicates that it is at least partially correlated with the Tamiami Formation of southern Florida (Ciampaglio and Osborn, Reference Ciampaglio and Osborn2011). However, the Tamiami Formation also shares many species with the UGCLS, including Lytechinus variegatus (Leske, Reference Leske1778); Mellita caroliniana (Ravenel, Reference Ravenel1842); Echinocardium orthonotum; Plagiobrissus sarae (Ciampaglio, Osborn, and Weaver, Reference Ciampaglio, Osborn and Weaver2009); Brissus glenni Cooke, Reference Cooke1959; and Agassizia porifera (Ravenel, Reference Ravenel1848) (Ciampaglio and Osborn, Reference Ciampaglio and Osborn2011; Osborn et al., Reference Osborn, Portell and Mooi2020). Therefore, the Tamiami Formation could be at least partially correlated with both the upper and lower portions of the Goose Creek Limestone (Ciampaglio and Osborn, Reference Ciampaglio and Osborn2011).

As the dominant Pliocene unit of southern Florida, the Tamiami Formation is underlain by Early Pliocene strata poorly represented in Florida due to the regression event mentioned above. The Early Pliocene is perhaps best represented in the upper portion of the Peace River Formation, but echinoids have not yet been documented there (Osborn et al., Reference Osborn, Portell and Mooi2020).

W.B. Clark and Twitchell (Reference Clark and Twitchell1915) and Mansfield (Reference Mansfield1932) described the first Pliocene echinoids of Florida, but additional collecting (enabled by significant quarrying activity fueled by the surge in population of the state throughout the twentieth century) expanded these records from three to 20 species (Osborn et al., Reference Osborn, Portell and Mooi2020). Strontium isotope dating provided an age of 2.79 to 4.70 Ma (Missimer, Reference Missimer, Zullo, Harris, Scott and Portell1993) and radiometric dating (U-Pb) produced an age of 2.99 ± 0.11 Ma (Klaus et al., Reference Klaus, Meeder, McNeill, Woodhead and Swart2017) for the Tamiami Formation, but these ages are still debated. Biostratigraphy, lithostratigraphy, and radiochronology provided age estimates from the Early to the Late Pliocene (Kier, Reference Kier1963; Missimer, Reference Missimer, Scott and Allmon1992; Waller, Reference Waller2018; Osborn et al., Reference Osborn, Portell and Mooi2020). Osborn et al. (Reference Osborn, Portell and Mooi2020) considered the Tamiami Formation as Late Pliocene, noting that with 15 species, it contains the richest echinoid fauna in the Neogene of Florida (Osborn et al., Reference Osborn, Portell and Mooi2020).

The Late Pliocene is represented in Florida by three additional units: the Intracoastal and Jackson Bluff formations, and the lower portion of the Nashua Formation. The Intracoastal Formation is an echinoid-rich unit (Scott, Reference Scott2001). Restricted to the Apalachicola Embayment of the south-central Florida panhandle (Huddleston, Reference Huddleston1976), it shares at least five echinoid species with the Tamiami Formation, including Arbacia improcera (see Osborn et al., Reference Osborn, Portell and Mooi2020).

The Upper Pliocene Jackson Bluff Formation is restricted to Leon, Liberty, and Wakulla counties of the Florida panhandle (Vernon and Puri, Reference Vernon and Puri1964). Although it has a rich and diverse molluscan assemblage, only three echinoid taxa are known, including A. improcera (see Osborn et al., Reference Osborn, Portell and Mooi2020).

The still poorly understood echinoids of the Nashua Formation were first documented by Oyen and Portell (Reference Oyen and Portell2001) and later summarized by Osborn et al. (Reference Osborn, Portell and Mooi2020). The unit likely contains both Late Pliocene and Early Pleistocene taxa, but the known specimens of Arbacia are unidentifiable to species (Osborn et al., Reference Osborn, Portell and Mooi2020).

Although only two species of Arbacia (A. improcera and A. percaribbeana new species) are known from the Pliocene of the region, the overlying Pleistocene contains three: A. waccamaw, A. rivuli, and A. punctulata. The latter are most common in two areas: southern Florida and the coastal plain of the Carolinas (Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019; Osborn et al., Reference Osborn, Portell and Mooi2020).

Oyen and Portell (Reference Oyen and Portell2001) noted a significant reduction in echinoid taxa in Florida from the Pliocene (20) to the Pleistocene (6), likely due to sampling and preservation biases, shorter duration of the Pleistocene, and other factors. This observed drop in diversity was challenged by stratigraphic revision at the base of the Pleistocene (Ogg et al., Reference Ogg, Ogg and Gradstein2008; Osborn et al., Reference Osborn, Portell and Mooi2020), resulting in 16 species of echinoid in the Pleistocene of Florida and 20 for the Pliocene. The addition of A. percaribbeana n. sp. increases the latter total to 21.

Pleistocene deposits in the southeastern USA

Southern Florida contains the richest Pleistocene echinoid faunas in North America. The Early Pleistocene of Florida is best represented in two units: the Caloosahatchee Formation, previously recognized as Upper Pliocene but reassigned to the lowermost Pleistocene (Ogg et al., Reference Ogg, Ogg and Gradstein2008), and the upper portion of the Nashua Formation, which contains Arbacia sp. The Caloosahatchee Formation is famous for its tropical to subtropical molluscan assemblage (Allmon et al., Reference Allmon, Emslie, Jones and Morgan1996) and the most diverse Pleistocene echinoid fauna of the region. We provide the first record of A. waccamaw from the formation, increasing the known number of Pleistocene echinoids in Florida to 17. This more complete picture of Pleistocene echinoid diversity is closer to that of the modern Floridian coastal fauna, with nine extant species (Osborn et al., Reference Osborn, Portell and Mooi2020).

The Middle Pleistocene of southern Florida is best illustrated by the Bermont Formation, which contains six echinoid species (Osborn et al., Reference Osborn, Portell and Mooi2020), but lacks known occurrences of Arbacia. Similar to the molluscan fauna of the unit, the echinoid fauna of the Bermont is decidedly modern. Only the cassiduloid, Rhyncholampas meansi Osborn, Portell, and Mooi, Reference Osborn, Portell and Mooi2020, is not represented in the Recent fauna of the region.

Well-exposed in eastern and southern Florida, the coastal Anastasia Formation contains A. punctulata (Herrera et al., Reference Herrera, Portell and Means2006; Osborn et al., Reference Osborn, Portell and Mooi2020). Murphy (Reference Murphy1973) used radiocarbon dating to suggest an age between 8.5–9.0 Ka for the type area on Anastasia Island, implying that at least some of the unit extends into the Holocene. Although no extinct molluscan taxa have been reported from the unit (Johnson, Reference Johnson1993), the cassiduloid R. meansi did not survive beyond the Pleistocene. It is likely that deposition of the formation continues today (Portell et al., Reference Portell, Turner and Beerensson2003).

The Early Pleistocene is represented in northeastern South Carolina and southeastern North Carolina by the Waccamaw Formation, which overlies the Upper Pliocene Goose Creek Limestone and outcrops as a narrow band stretching from Wilmington, North Carolina to Myrtle Beach, South Carolina (L. Campbell et al., Reference Campbell, Campbell, Colquhoun, Ernissee and Abbott1975). All occurrences are restricted to within 100 ft (30.5 m) of present mean sea level and no more than 75 mi (120.7 km) inland from the Atlantic (DuBar and Furbunch, Reference DuBar and Furbunch1965). The molluscan fauna of the Waccamaw Formation shares many similarities with the correlative Caloosahatchee Formation of southern Florida (DuBar, Reference DuBar1971; L. Campbell et al., Reference Campbell, Campbell, Colquhoun, Ernissee and Abbott1975; DuBar and DuBar, Reference DuBar and Dubar1980), but the echinoids are distinct. Both units contain 10 species (Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019; Osborn et al., Reference Osborn, Portell and Mooi2020), but only A. waccamaw, L. variegatus, and A. porifera occur in both. Lytechinus variegatus is comparatively rare within the Waccamaw, and A. waccamaw is equally rare in the Caloosahatchee Formation.

There is a significant lithological distinction between the Upper Pliocene sandy gray limestone of the uppermost Goose Creek Limestone, which is capped with an indurated bed, and the overlying shelly marls of the Lower Pleistocene Waccamaw Formation in Horry County, South Carolina, but there are few changes in the echinoid fauna across the transition. Mellita caroliniana, A. waccamaw, and Rhyncholampas sabistonensis (Kellum, Reference Kellum1931) are abundant in both units on either side of the indurated bed separating them in Horry County (Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019). The uppermost Goose Creek Limestone and Lower Waccamaw Formation also share A. porifera, L. variegatus, and B. glenni. Although A. waccamaw occurs in both the Upper Pliocene and Lower Pleistocene strata of the Carolinas, A. rivuli appears to be restricted to a very narrow stratigraphic horizon in the lowermost Waccamaw Formation in its type area in Horry County, South Carolina (Osborn and Ciampaglio, Reference Osborn and Ciampaglio2019).

The Waccamaw Formation is overlain by the Middle to Upper Pleistocene Canepatch Formation (DuBar, Reference DuBar1971), erected for a complex of sand, clay, silt, and peat deposits exposed along the Intracoastal Waterway in Horry County, South Carolina, and southeastern North Carolina. Bybell (Reference Bybell1990) stated that the Canepatch was deposited 450 Kya, and Lyons (Reference Lyons1991) asserted its correlation with the Upper Pleistocene Fort Thompson Formation of southern Florida. The Canepatch Formation contains abundant Mellita isometra Harold and Telford, Reference Harold and M. Telford1990 and Encope michelini Agassiz, Reference Agassiz1841, as well as rare occurrences of A. punctulata, which is usually represented by loose spines and test fragments.

Finally, Arbacia is found in the Upper Pleistocene Wando Formation at Simmons’ Bluff, which Holmes (Reference Holmes1849) described as the most extensive exposure of post-Pliocene strata in the Charleston, South Carolina area. The bluff, now covered, is on Yonges Island, 25 mi (40.2 km) southwest of Charleston on Wadlamaw Sound. Anapesus carolinus Holmes, Reference Holmes1860, described from the unit, was synonymized by Mortensen (Reference Mortensen1935) with A. punctulata, which occurs in the shell beds of Simmons’ Bluff. The Wando Formation includes strata previously attributed to the Pamlico Formation (Cooke, Reference Cooke1937) and Princess Anne Terrace (McCartan et al., Reference McCartan, Weems, Lemon, Sohl and Wright1980); McCartan (Reference McCartan1990) provided a Late Pleistocene age of 70–130 Ka for the unit.

Stratigraphic formations in the West Indies

The occurrence of Arbacia in the West Indies is poorly known. Donovan and Paul (Reference Donovan, Paul, Emson, Smith and Campbell1996, Reference Donovan and Paul1998) mentioned Arbacia sp. indet. from the Pliocene Bowden Formation in Jamaica (Donovan and Paul, Reference Donovan and Paul1998, pl. 2, figs. 2, 8, pl. 3, figs. 1–4, 6), and it was again referred to by Donovan (Reference Donovan2001), Donovan et al. (Reference Donovan, Portell and Veltkamp2005), Donovan and Portell (Reference Donovan and Portell2013), and Donovan et al. (Reference Donovan, Pickerill and Keighley2014). The material illustrated by Donovan and Paul (Reference Donovan and Paul1998) can be referred to as Lytechinus cf. L. variegatus. The specimen (NHMUK PI EE 5215-2) illustrated by Donovan et al. (Reference Donovan, Pickerill and Keighley2014) is also not an Arbacia, as evidenced by the spine structure and tubercle position. Other UF material from Jamaica does not belong to the genus Arbacia (UF 67430 and 108340 are too small to identify).

Donovan (Reference Donovan2003) mentioned an arbaciid from the Lower Pleistocene Manchioneal Formation in Jamaica. Donovan and Embden (Reference Donovan and Embden1996, fig. 2.9) depicted an internal mold (NHMUK PI EE 5102) with poor preservation. Additional material (NHMUK PI EE 5103, 5104) was also mentioned, but allocations remain uncertain (Donovan and Embden, Reference Donovan and Embden1996). Donovan et al. (Reference Donovan, Jones and Harper2016) also noted an ‘Arbacia? sp.’ from the Middle Miocene Cayman Formation of the Cayman Islands. The specimen (UA PI669) is a poorly preserved, small internal mold (< 15 mm) of uncertain affinities. Spines (e.g., UF 134468, 134901) from the Late Pleistocene Jaimanitas Formation of Cuba, can be attributed to Arbacia, because they are indistinguishable from those of A. punctulata, found rarely around Cuba.

Stratigraphic formations in Venezuela

The northwestern region of Venezuela (Falcón State) has fossil-rich upper Neogene deposits. These are extensively studied due to large, mostly terrestrial vertebrates, including crocodiles, xenarthrans, and testudines (Scheyer et al., Reference Scheyer, Aguilera, Delfino, Fortier, Carlini, Sánchez, Carrillo-Briceño, Quiroz and Sánchez-Villagra2013; Carrillo-Briceño et al., Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021). The San Gregorio Formation, which is the youngest unit of the Urumaco stratigraphic section (Scheyer et al., Reference Scheyer, Aguilera, Delfino, Fortier, Carlini, Sánchez, Carrillo-Briceño, Quiroz and Sánchez-Villagra2013), is well-exposed in northwestern Venezuela near the town of Urumaco, where it crops out for 570 m (Carrillo-Briceño et al., Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021).

The San Gregorio Formation was first subdivided into the Río Seco conglomerate, corresponding to the upper part of the formation, and a lower unnamed portion composed of uniform siltstones. Stainforth (Reference Stainforth1962) later subdivided the latter portion into two units based on fossil beds in its upper layers, the Vergel and Cocuiza members. The former covers the lowermost part of the San Gregorio Formation, spanning 350 m at the type section (Stainforth, Reference Stainforth1962), and is conformably overlain by the Cocuiza Member (Vucetich et al., Reference Vucetich, Carlini, Aguilera and Sánchez-Villagra2010). The Río Seco Member forms the uppermost part of the San Gregorio. Unlike others of the formation, the Cocuiza Member is composed of coastal marine sediments deposited under conditions of low to moderate energy (Mihaljevič et al., Reference Mihaljević, Klug, Aguilera, Lüthi and Sánchez–Villagra2010; Carrillo-Briceño et al., Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021).

Age of the San Gregorio Formation was originally believed to be Early Pliocene (Rey, Reference Rey1990; Hambalek et al., Reference Hambalek, Rull, De Digiacomo and Díaz de Gamero1994). Carrillo et al. (Reference Carrillo, Amson, Jaramillo, Sánchez, Quiroz, Cuartas, Rincón and Sánchez-Villagra2018) proposed an age of ~ 1.8 Ma (Early Pleistocene) for the base of the formation, based on foraminiferan and nannoplankton assemblages, and magnetostratigraphy. The foraminiferans are poorly preserved and largely reworked specimens, unlike the nannoplankton assemblage that was dated to the early Pleistocene. ⁸⁷Sr/⁸⁶Sr geochronological analyses indicated an age ranging 1.59 ± 0.05 to 1.38 ± 0.06 Ma (Carrillo-Briceño et al., Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021).

Specimens of A. percaribbeana n. sp. include UCMP 38200 (Linder et al., Reference Linder, Durham and Orr1988), collected by J.O. Nomland and L.W. Henry in 1931 from the San Gregorio Formation, Falcón State, Venezuela (UCMP locality S-18), ~ 2 km north of the Rio Seco Road of the Creole Petroleum Company. This is close to locality SRS-A of Carrillo-Briceño et al. (Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021), at which the pumping station of the Creole Petroleum Company is mentioned, ~ 2 km south of the locality (Fig. 1). This locality provided an additional 18 specimens (UCMP 134665).

Figure 1.

Distribution of study material of Arbacia percaribbeana n. sp. in Florida, Venezuela, and the Lesser Antilles: (1) type locality in Florida, USA (yellow star); (2) known distribution in Venezuela and the Lesser Antilles (blue stars).

Figure 1. Long description

A two-panel map set.

Panel 1: A large-scale map of the Americas. A yellow star marks the type locality in Florida, USA. A red bounding box highlights the northern region of South America, specifically Venezuela. The Atlantic Ocean is labeled to the Northeast, the Pacific Ocean to the Southwest, and South America at the center.

Panel 2: A detailed inset of the region within the red box. The map shows Venezuela in grey, bordered by Colombia to the West and Brazil to the South. Specific locations are marked with blue stars and labels:

* In the Northwest, a blue star is located in the Falcon State, which is highlighted in dark red.

* North of Falcon State, a blue star marks Curaçao.

* Moving East along the coast, a blue star marks Cubagua.

* In the Northeast, the island of Trinidad is highlighted in dark red with a blue star.

* North of Trinidad, a blue star marks Tobago.

A scale bar indicating 100 km and a North arrow are located at the bottom left of the panel.

Most specimens of the new species were collected in proximity to Urumaco (Falcón State, Venezuela), but without specific locality information. USNM PAL 805807 was collected near Rio Codore, below Urumaco; USNM PAL 805802 originated from eastern Falcón State, NW Venezuela; and USNM PAL 805803 was collected in Falcón State, Venezuela. Another specimen (USNM PAL 805805) was collected along Rio Seco, northeast of Urumaco, potentially corresponding to the locality SRS-A/B of Carrillo-Briceño et al. (Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021), which is recognized as part of the Cocuiza Member containing a marine fauna.

A specimen identified as A. punctulata (see Mihaljevič et al., Reference Mihaljević, Klug, Aguilera, Lüthi and Sánchez–Villagra2010) is here referred to A. percaribbeana n. sp. It was collected in the locality of Cocuiza West (11°18’38.4"N; 70°14’26.2"W) in the Cocuiza Member of the San Gregorio Formation (Mihaljevič et al., Reference Mihaljević, Klug, Aguilera, Lüthi and Sánchez–Villagra2010), corresponding to locality NCH-B (Northward Chiguaje Hill) of Carrillo-Briceño et al. (Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021), where the typical Cocuiza Member crops out (Carrillo-Briceño et al., Reference Carrillo-Briceño, Sánchez, Scheyer, Carrillo and Delfino2021).

USNM PAL 805806 comes from Cubagua Island (Venezuela) at which Neogene deposits are well-known. This is the only specimen identified from this locality. The Cubagua Group ranges from Late Miocene to Early Pleistocene (lower Gelasian; Landau et al., Reference Landau, Vermeij and da Silva2008).

USNM PAL 805804 comes from the Middle Pliocene (Piacenzian) Springvale Formation of Trinidad (Gazalie et al., Reference Gazalie, Lakhan and Archie2016), from Savonetta near Gran Couva, Savaneta River area, 1,700 ft (518 m) southwest of Philippine Estate, Bicchiu Castle Estate.

Donovan (Reference Donovan2001) identified Arbacia (NHMUK E 82828-9; 82880) from the coastal exposure at Rockly Bay Tobago, west of Scarborough, in the Balanus Bed (Bed 2) of the Rockly Bay Formation that Lewis and Donovan (Reference Lewis and Donovan1991) assigned to Arbacia improcera. The present work provides the first figures of these specimens, showing closer affinities with Arbacia percaribbeana n. sp. Although the formation is poorly documented, recent work suggests that it is Middle Pliocene (Donovan, Reference Donovan1989; Weber et al., Reference Weber, Arkle, Giorgis and Hippolyte2014; Hippolyte and Mann, Reference Hippolyte and Mann2021).

Fossils identified as Arbacia (UF 230081) from the Pliocene Seroe Domi Formation, Savarese Unit D of Curaçao are attributed to Arbacia percaribbeana n. sp. A previously collected specimen from the Seroe Domi Formation of Curaçao, identified as Arbacia waccamaw and illustrated by de Buisonjé (Reference de Buisonjé1974), is also referred to A. percaribbeana n. sp.

Material identified as Arbacia in earlier work but now assigned to A. percaribbeana n. sp. is listed in Table 1.

Table 1.

Reassignment of previously identified material to Arbacia percaribbeana n. sp.

Table 1. Long description

The table consists of eight rows of data under four headers.

Row 1: Arbacia sp. indet.; U C M P 38200, Linder and Durham 1988; San Gregorio Formation, Falcón State, Venezuela, UCMP locality S-18; Collected from the same fossil zone as additional material with consistent morphology.

Row 2: A. punctulata; Specimen figured by Mihaljevič et al. 2010; Cocuiza West, San Gregorio Formation, Venezuela; Locality and morphology consistent with the new species.

Row 3: Arbacia sp. indet.; U S N M P A L 805802, 805803, 805805, 805807; Falcón State and Urumaco region, Venezuela; Material from the same regional Pliocene-Pleistocene assemblage with matching morphology.

Row 4: Arbacia sp. indet.; U S N M P A L 805806; Cubagua Island, Venezuela; Consistent morphology.

Row 5: A. punctulata; U S N M P A L 805804; Springvale Formation, Trinidad; Morphology and age fit the new species.

Row 6: A. improcera; N H M U K E 82828, 82829, 82880; Rockly Bay Formation, Tobago, Balanus Bed; Re-examination shows closer affinity with the new species.

Row 7: Arbacia sp. indet. or A. waccamaw; U F 230081, de Buisonjé 1974 material; Seroe Domi Formation, Curaçao, Savarese Unit D; Specimens attributable based on morphology.

Row 8: Arbacia improcera; U F 289212, Osborn et al. 2020; Tamiami Formation; Specimens attributable based on morphology.

Diagnosis

Mortensen (Reference Mortensen1935) provided an excellent description, but not a diagnosis in the sense that we use it elsewhere in the present work, so we have adapted it by excluding many features that are descriptive but not unique the Arbaciidae.

Arbacioids with compound plates in ‘arbacioid’ configuration, i.e., usually trigeminate, but rarely simple or polyporous. Tubercles imperforate, smooth, with ambulacral primary tubercles generally not smaller than those at interambulacral ambitus; the latter can be numerous, arranged in both horizontal and vertical series. Aboral side of test can be naked, lacking tubercles (and therefore, spines). Test usually carrying several epistromal papillae not bearing spines. Primordial interambulacral plate persistent throughout ontogeny, often conspicuously elongated, bearing a primary tubercle. Apical system usually dicyclic, but oculars partly insert in some taxa. Ocular pores usually double. Periproct covered by four or five large, triangular valves. Peristome often very large, variably covered with nonambulacral scales, sometimes naked. Buccal notches usually distinct. Primary spines with more or less developed cortical layer, which can be lacking on aboral spines; spines usually smooth, not thorny. Secondary spines little developed, can be totally lacking; when present, simple or club-shaped, not flattened, or scale-like. Pedicellariae tridentate, triphyllous and ophicephalous; stalk consisting of numerous filaments, not connected except distally. Sphaeridia usually in deep pits in ambulacral midline. Spicules in soft tissues often present as straight rods, widened and with a few central holes.

Genus Arbacia Gray, Reference Gray1835

Type species

Arbacia lixula Linnaeus, Reference Linnaeus1758. Distribution and occurrences provided by Courville et al. (Reference Courville, Poulin, Saucède, Mooi, Lessios, Martinez Salinas and Diaz2023c).

Diagnosis

Arbaciidae with ocular plates bearing small tubercle, usually resorbed during ontogeny; periproct slightly elongated in direction 1–IV and covered with four supra-anal plates; ocular pores double, not visible externally; peristome large (> 30% TD), ambulacra protruding to form ‘ambulacral lips’; buccal notches shallow, wide; tags narrow, more or less elongated; oral primary spines with cortex-layer ‘shoe’ or ‘cap’; ambital and upper spines without any cortex-layer; sphaeridia single, in small pit close to peristomial edge; epistroma conspicuously developed, can be of characteristic design, forming randomly distributed punctation, or arranged in horizontal or vertical series (Courville et al., Reference Courville, Poulin, Saucède, Mooi, Lessios, Martinez Salinas and Diaz2023c).

Arbacia punctulata (Lamarck, Reference Lamarck1816)

Figures 2, 3

Figure 2.

Fossil Arbacia punctulata (Lamarck, Reference Lamarck1816), Upper Pleistocene Anastasia Formation, Florida, USA: (1–3) UF 330485: (1) aboral view; (2) interambulacrum in lateral view; (3) ambulacrum in lateral view; (4) UF 324794, aboral view; (5, 6) UF 112190: (5) aboral view; (6) oral view. Scale bars = 10 mm.

Figure 2. Long description

A multi-panel photo containing six views of fossilized sea urchins.

* Panel 1 at the top-left shows an aboral view of specimen U F 330485, featuring a circular central opening and five radiating ambulacral segments separated by wider interambulacral areas covered in rounded tubercles.

* Panel 2 at the top-center shows a lateral view of the same specimen, focusing on the interambulacrum which displays large, prominent tubercles arranged in vertical rows.

* Panel 3 at the top-right shows a lateral view of the ambulacrum, characterized by smaller, more densely packed pore pairs and tubercles.

* Panel 4 at the bottom-left shows an aboral view of specimen U F 324794, highlighting the pentameral symmetry and the hexagonal plates of the test.

* Panel 5 at the bottom-center shows an aboral view of specimen U F 112190, similar in structure to panel 1 but with slightly different preservation of the surface texture.

* Panel 6 at the bottom-right shows the oral view of specimen U F 112190, revealing a large, irregular central opening where the Aristotle’s lantern would have been located, surrounded by the tuberculated test.

White scale bars representing 10 mm are located at the bottom-right of panels 2, 4, and 6.

Figure 3.

Arbacia punctulata (Lamarck, Reference Lamarck1816), details of test plating: (1) UF 112190, apical system; (2) UF 112190, aboral plates of interambulacrum; (3) USNM PAL 805809, aboral plates of ambulacrum. Scale bars = 10 mm (1, 2); 5 mm (3).

Figure 3. Long description

The figure consists of three panels labeled 1 through 3 from left to right.

* Panel 1 shows the apical system of U F 112190. At the center is a large, dark, pentagonal periproct. Surrounding this core are five genital plates. One plate in the upper right is larger and covered in fine stippling, representing the madreporite. Each plate contains a small circular pore near its outer edge. A 10 mm scale bar is positioned at the bottom right.

* Panel 2 displays the aboral plates of the interambulacrum of U F 112190. The structure is triangular, tapering toward the top. It consists of two vertical columns of interlocking hexagonal plates. Each plate features a prominent circular tubercle at its center, with smaller secondary tubercles scattered around the base. A 10 mm scale bar is at the bottom right.

* Panel 3 illustrates the aboral plates of the ambulacrum of U S N M P A L 805809. The structure shows two large primary tubercles on the right side, each surrounded by a smooth circular area. To the left of these are vertical rows of smaller, dark circular pore pairs. A 5 mm scale bar is located at the bottom right.

Holotype

One known syntype MNHN EcEs 5001. This specimen is broken and mixed in the same sample with another echinoid species, probably Caenocentrotus gibbosus (L. Agassiz in L. Agassiz and Desor, Reference Agassiz and Desor1846).

Occurrence

Fossil occurrences are known from Florida (USA), South Carolina (USA), Virginia (USA), and French Guiana. Upper Pleistocene Anastasia Formation (Herrera et al., Reference Herrera, Portell and Means2006; Osborn et al., Reference Osborn, Portell and Mooi2020), Upper Pleistocene Canepatch Formation (Ciampaglio et al., Reference Ciampaglio, Osborn and Weaver2009), Upper Pleistocene Wando Formation, Late Pleistocene of Virginia, Upper Pleistocene Norfolk Formation, and Late Pleistocene (130–115 Ka; Antoine et al., Reference Antoine, Wieringa, Adnet, Aguilera and Bodin2024) of French Guiana.

Remarks

Based on morphology (Figs. 2, 3), the fossil material studied from Florida, South Carolina, and Virginia seems to be closely related to specimens of A. punctulata from the eastern coast of the USA (Courville et al., Reference Courville, Mongiardino Koch, Jossart, Moreau and Mooi2025).

Arbacia improcera (Conrad, Reference Conrad1843a)

Figures 4–7

Figure 4.

Morphology of Arbacia improcera (Conrad, Reference Conrad1843a): (1–4) USNM PAL 474032: (1) apical view; (2) oral view; (3, 4) oblique views; (5) UF 40402, oblique view; (6, 7) UF 21408: (6) apical view; (7) lateral view; (8, 9) UF 28205: (8) apical view; (9) oblique view; (10) UF 10086, oblique view. Scale bars = 10 mm.

Figure 4. Long description

A collection of ten photographs of sea urchin fossils. Each specimen features a hemispherical or dome-shaped test covered in rows of small, rounded tubercles.

* Panel 1 shows specimen U S N M P A L 474032 from the top apical view, revealing a central circular opening and radiating patterns.

* Panel 2 shows the same specimen from the bottom oral view, featuring a large central aperture.

* Panels 3 and 4 provide oblique side views of the same specimen, highlighting the height of the dome and the vertical rows of tubercles.

* Panel 5 is an oblique view of specimen U F 40402.

* Panel 6 shows specimen U F 21408 from the apical view, with a clearly defined central apical disc.

* Panel 7 is a lateral profile of the same specimen, showing a flatter, low-dome shape.

* Panel 8 shows specimen U F 28205 from the apical view.

* Panel 9 is an oblique view of the same specimen.

* Panel 10 shows specimen U F 10086 in an oblique view, partially embedded in or attached to a piece of light-colored matrix rock.

White scale bars representing 10 mm are positioned at the bottom right of most panels.

Figure 5.

Arbacia improcera (Conrad, Reference Conrad1843a): (1) UF 101103, apical view; (2) USNM PAL 474029, apical view; (3) USNM PAL 474017, apical view; (4–7) UF 238568: (4) apical view; (5) oral view; (6, 7) lateral views; (8) UF 205196, apical view; (9) UF 232267, oblique view; (10) UF 110409, oblique view; (11) UF 289215, apical view. Scale bars = 10 mm.

Figure 5. Long description

A multi-panel display of fossilized sea urchin tests.

* Panel 1: Apical view of U F 101103, showing a circular test with a central hole and radiating rows of small tubercles.

* Panel 2: Apical view of U S N M P A L 474029, featuring a pinkish hue on the lower half and a handwritten catalog number.

* Panel 3: Apical view of U S N M P A L 474017, a light cream-colored specimen with distinct vertical catalog numbering.

* Panel 4: Apical view of U F 238568, showing a slightly weathered surface.

* Panel 5: Oral view of U F 238568, displaying the underside with a large central opening and a white label.

* Panels 6 and 7: Lateral views of U F 238568, showing the low, dome-like profile and the bumpy texture of the tubercles along the sides.

* Panel 8: Apical view of U F 205196, a larger, more encrusted specimen with a prominent central apical opening.

* Panel 9: Oblique view of U F 232267, showing the test from an angled perspective to highlight the curvature.

* Panel 10: Oblique view of U F 110409, similar to panel 9 but with a more yellowish tint.

* Panel 11: Apical view of U F 289215, showing a well-preserved symmetrical arrangement of ambulacral and interambulacral areas.

White scale bars representing 10 mm are placed near the bottom right of most panels to indicate size.

Figure 6.

Arbacia improcera (Conrad, Reference Conrad1843a), intraspecific diversity and details of test plating: (1) UF 21408, apical system; (2, 3) USNM PAL 474032: (2) aboral plates of interambulacrum; (3) aboral plates of ambulacrum; (4–6) USNM PAL 642133: (4) apical system; (5) aboral plates of interambulacrum; (6) aboral plates of ambulacrum. Scale bars = 10 mm (2, 5); 5 mm (1, 3, 4, 6).

Figure 6. Long description

A multi-panel scientific illustration containing six numbered panels arranged in two rows.

Panel 1 shows the apical system of specimen U F 21408. At the center are four triangular periproctal plates forming a closed diamond shape, surrounded by a ring of five larger genital plates and five smaller ocular plates. One genital plate features a dense cluster of small pores. A 5 mm scale bar is at the bottom right.

Panel 2 displays the aboral plates of the interambulacrum for specimen U S N M P A L 474032. It shows a vertical column of interlocking trapezoidal plates with circular tubercles along the outer edges. A 10 mm scale bar is at the bottom right.

Panel 3 shows a close-up of the aboral plates of the ambulacrum for specimen U S N M P A L 474032, featuring two large primary tubercles with central pits and numerous smaller secondary pores. A 5 mm scale bar is at the bottom right.

Panel 4 illustrates the apical system of specimen U S N M P A L 642133. It features a large, dark, asymmetrical central opening surrounded by five large genital plates, each containing a single distinct pore. A 5 mm scale bar is at the bottom right.

Panel 5 shows the aboral plates of the interambulacrum for specimen U S N M P A L 642133. Similar to panel 2, it depicts a tapered column of plates with small circular tubercles concentrated at the base and along the margins. A 10 mm scale bar is at the bottom right.

Panel 6 provides a detail of the aboral plates of the ambulacrum for specimen U S N M P A L 642133, showing one large, prominent tubercle at the bottom right and several smaller pores and tubercles scattered across the plate surface. A 5 mm scale bar is at the bottom right.

Figure 7.

Arbacia improcera (Conrad, Reference Conrad1843a), lowermost upper Goose Creek Limestone, South Carolina, USA (TD ranging 42–48 mm): (1) UF 356362, oblique view; (2, 3) UF 356359: (2) apical view; (3) lateral view; (4) UF 356361, lateral view; (5, 6) UF 356360: (5) apical view; (6) oblique view; (7) UF 356370, apical view. Scale bars = 10 mm.

Figure 7. Long description

A collection of seven photographs of fossilized echinoid tests, each accompanied by a white 10 mm scale bar.

* Panel 1 shows specimen U F 356362 in an oblique view, highlighting the rounded, dome-like shape and the bumpy texture of the primary tubercles.

* Panel 2 shows specimen U F 356359 in an apical view, looking directly down at the top of the test. Five distinct ambulacral segments radiate from the central apical system like a star.

* Panel 3 shows the same specimen, U F 356359, in a lateral view, emphasizing the height and the concentration of large tubercles around the midsection.

* Panel 4 shows specimen U F 356361 in a lateral view, displaying a slightly flatter profile compared to panel 3.

* Panel 5 shows specimen U F 356360 in an apical view. The five-fold symmetry is very clear, with rows of small pores visible along the ambulacral paths.

* Panel 6 shows the same specimen, U F 356360, in an oblique view, showing the transition from the top surface to the side.

* Panel 7 shows specimen U F 356370 in an apical view, featuring a more weathered or calcified surface texture while maintaining the radial symmetry.

All specimens exhibit a characteristic pattern of raised nodes (tubercles) and fine pore pairs arranged in vertical columns.

Reference Conrad1843a Echinus improcerus Conrad, p. 310.

Reference Stefanini1911 Psammechinus improcerus; Stefanini, p. 705.

Reference Clark and Twitchell1915 Coelopleurus improcerus; W.B. Clark and Twitchell, p. 180, pl. 84, figs. 4a–c.

Reference Clark and Twitchell1915 Coelopleurus sloani W.B. Clark in W.B. Clark and Twitchell, p. 181, pl. 84, figs. 5a, b.

Reference Cooke1941 Arbacia sloani; Cooke, p. 11.

Reference Cooke1941 Arbacia improcera; Cooke, p. 11, pl. 1, figs. 7–9.

Reference Cooke1959 Arbacia improcera; Cooke, p. 20, pl. 4, figs. 1–3.

Reference Cooke1959 Arbacia sloani; Cooke, p. 21, pl. 4, figs. 12–14.

Reference Kier1963 Arbacia improcera; Kier, p. 14, pl. 1, figs. 1–5.

Reference Kier1963 Arbacia crenulata Kier, p. 11, pl. 1, figs. 1–15, text figs. 3–7.

Reference Kier1972 Arbacia improcera; Kier, p. 8, pl. 1.

Reference Kier1972 Arbacia sloani; Kier, p. 8, pl. 2, fig. 1.

Reference Kier1983 Arbacia improcera; Kier, p. 501, pl. 1, fig. 6.

Reference Ciampaglio, Osborn and Weaver2009 Arbacia improcera; Ciampaglio et al., fig. 2.

Reference Osborn, Portell and Mooi2020 Arbacia improcera; Osborn et al., figs. 14, 15.

Type specimens

The material, probably originally housed at ANSP according to Cooke (Reference Cooke1941), has been lost (A. Martinez-Melo, collection manager of Invertebrate Paleontology, ANSP, personal communication, January 2023). Specimen USNM PAL 166487, figured by W.B. Clark and Twitchell (Reference Clark and Twitchell1915), Cooke (Reference Cooke1959), and Kier (Reference Kier1963), is herein designated as the neotype (see below).

Emended diagnosis

Arbacia with tubercle on each ocular and genital plate usually, but not always completely resorbed during ontogeny; single, often discontinuous perradial column of primary tubercles aborally in interambulacrum; interambulacral granules often present interradially; numerous interambulacral plates (N = 13 at TD = 20 mm); ambulacral tubercles poorly developed aborally.

Occurrence

Known from Florida, Georgia, South and North Carolina, and Virginia, USA. The specimen described by Conrad (Reference Conrad1843a) came from James River, near Smithfield, Virginia. Kier (Reference Kier1963) listed additional localities within the Tamiami Formation (Osborn et al., Reference Osborn, Portell and Mooi2020). The designated neotype comes from the middle to upper Pliocene Yorktown Formation at J.T. Williams’ marl pit, Smith Creek, 0.5 mi (0.8 km) below Suffolk, Virginia. Type material derives from the Middle to Upper Pliocene Yorktown Formation of Virginia. Additional specimens can be found in the lower Goose Creek Limestone and the lowermost upper Goose Creek Limestone of North Carolina, the Upper Pliocene Tamiami Formation of Florida, and the Pliocene of Georgia.

Description

Remarks

Comparison with other species of Arbacia

This species differs from all other Arbacia except A. rivuli and A. waccamaw by the presence of an interambulacral inner tubercle aborally that is the same size as the primary tubercles and abutting the interradial suture, and a tubercle on each ocular and genital plate that is not always completely resorbed during ontogeny. It differs from A. rivuli and A. waccamaw in having a higher number of interambulacral plates (10 at TD = 20 mm in A. waccamaw, and no more than 9 at TD = 20 mm in A. rivuli, whereas usually 12 at TD = 20 mm in A. improcera).

Arbacia rivuli Cooke, Reference Cooke1941

Figures 8–10

Figure 8.

Arbacia rivuli Cooke, Reference Cooke1941, holotype, USNM PAL 498887, Lower Pleistocene Waccamaw Formation, South Carolina, USA: (1) apical view; (2) oblique view. Scale bar = 10 mm.

Figure 9.

Arbacia rivuli Cooke, Reference Cooke1941, details of test plating: (1) UF 203039, apical system; (2) UF 203037, aboral plates of interambulacrum; (3) USNM PAL 805813, aboral plates of ambulacrum. Scale bars = 10 mm (1, 2); 5 mm (3).

Figure 9. Long description

A multi-panel line drawing containing three numbered sections.

* Panel 1 shows the apical system of U F 203039. At the center is a large, dark, irregular pentagonal opening. Surrounding this core are five primary plates. Each plate contains a circular pore. The top-right plate is distinguished by a dense stippled texture. A 10 mm scale bar is located at the bottom right.

* Panel 2 displays the aboral plates of the interambulacrum of U F 203037. The plates are arranged in two vertical columns that taper toward the top. Each plate features a prominent circular tubercle with a central ring. A 10 mm scale bar is at the bottom right.

* Panel 3 illustrates the aboral plates of the ambulacrum of U S N M P A L 805813. It shows two columns of plates. The left column contains pairs of dark, oval-shaped pores connected by dashed lines. The right column features a single large circular tubercle at the bottom and smaller pores above it. A 5 mm scale bar is at the bottom right.

Figure 10.

Arbacia rivuli Cooke, Reference Cooke1941, UF 350877, basal bed of the Lower Pleistocene Waccamaw Formation, Intracoastal Waterway, northeast of Grand Strand Airport, North Myrtle Beach, Horry County, South Carolina, USA: (1) apical view; (2) oral view; (3) lateral view; (4, 5) oblique views. Scale bars = 10 mm.

Figure 10. Long description

A multi-panel photo set of a fossilized sea urchin test.

* Panel 1 at the top-left shows the apical view. At the center is a circular opening surrounded by five smaller pores. Radiating outward are five double-rows of small pores alternating with sections of larger rounded bumps. A 10 mm scale bar is located at the bottom right of this panel.

* Panel 2 at the top-center shows the oral view. It features a large, jagged circular opening at the center revealing a dark interior. The surrounding surface is covered in dense, rounded tubercles.

* Panel 3 at the top-right shows the lateral view. The fossil has a low, dome-like profile with a flat base. The surface texture of tubercles and pore rows is visible across the curve. A 10 mm scale bar is at the bottom right.

* Panel 4 at the bottom-left shows an oblique view. The perspective is angled to show both the top and side, highlighting the three-dimensional arrangement of the pore rows and the height of the tubercles.

* Panel 5 at the bottom-right shows a second oblique view from a slightly different angle, emphasizing the symmetry of the five-fold radial segments. A 10 mm scale bar is positioned at the bottom center between panels 4 and 5.

Reference Cooke1941 Arbacia rivuli Cooke, p. 10, pl. 1.

Reference Cooke1959 Arbacia rivuli; Cooke, p. 20, pl. 4, figs. 10, 11.

Holotype

USNM PAL 498887 (Fig. 8). Specimen is complete, preserved without spines, but with all diagnostic characters recognizable. Only one ambulacrum and one interambulacrum are completely prepared. The apical system is complete but not entirely visible. The specimen dimensions are TD = 32.5 mm; TH = 18.5 mm; PD = 16.5 mm.

Emended diagnosis

Arbacia in which ocular plates have one large tubercle (TD = 40 mm); number of interambulacral plates very low (N = 11 to 12 plates at TD = 40 mm); second column of interambulacral inner tubercle abutting interradius suture aborally; ambulacral tubercles irregularly developed aborally.

Occurrence

Arbacia rivuli occurs only at the type locality (Horry County, South Carolina) at the boundary between the uppermost Pliocene (upper Goose Creek Limestone) and the lowermost Pleistocene Waccamaw Formation. The type specimen comes from the Intracoastal Waterway canal, 4.5 mi (7.2 km) southwest of Little River, Horry County, South Carolina (USNM station 13377). Waccamaw Formation, Early Pleistocene.

Description

Remarks

Comparison with other species of Arbacia

This species differs from all other Arbacia spp., except for A. waccamaw, by the presence of large tubercles on the ocular plates in large adult specimens. It differs from A. waccamaw and A. improcera in having a much lower number of interambulacral plates and a second column of interambulacral tubercles in the interradial area.

Arbacia waccamaw Cooke, Reference Cooke1941

Figures 11–13

Figure 11.

Arbacia waccamaw Cooke, Reference Cooke1941, holotype, USNM PAL 498888, Lower Pleistocene Waccamaw Formation, South Carolina, USA: (1) apical view; (2) oblique view. Scale bar = 10 mm.

Figure 12.

Arbacia waccamaw Cooke, Reference Cooke1941, UF 105636, details of test plating: (1) apical system; (2) aboral plates of interambulacrum; (3) aboral plates of ambulacrum. Scale bars = 10 mm (2); 5 mm (1, 3).

Figure 12. Long description

The illustration consists of three panels labeled 1 through 3 from left to right.

Panel 1 shows the apical system. At the center is a large, black, circular periproct. Surrounding this core are five large genital plates arranged in a ring. Each plate features a circular gonopore near its outer edge. Small, dark ocular plates are wedged between the genital plates at the perimeter. A scale bar at the bottom right represents 5 mm.

Panel 2 displays the aboral plates of the interambulacrum. The plates are arranged in two vertical columns that meet at a central zigzag suture line, forming a triangular shape that widens toward the base. Each plate contains a large, circular primary tubercle near the outer margin. A scale bar at the bottom right represents 10 mm.

Panel 3 illustrates the aboral plates of the ambulacrum. It shows two columns of plates. The left side features pairs of small, dark pore pairs arranged vertically. The right side shows larger plates with a single, very large primary tubercle at the bottom and smaller secondary tubercles and granules above it. A scale bar at the bottom right represents 5 mm.

Figure 13.

Arbacia waccamaw Cooke, Reference Cooke1941, Lower Pleistocene Caloosahatchee Formation, Florida, USA: (1–4) UF 105636: (1) apical view; (2) oral view; (3, 4) lateral views; (5–8) UF 14131: (5) apical view; (6) oral view; (7, 8) lateral views. Scale bars = 10 mm.

Figure 13. Long description

The photo displays two fossilized echinoid tests against a black background.

Top row (Specimen U F 105636):

- Panel 1 (Top-Left): Apical view showing a circular, dome-shaped test with five radiating ambulacral areas. The surface is covered in small, rounded tubercles. A central hole marks the apical system.

- Panel 2 (Top-Center): Oral view showing the underside. A large circular opening at the center contains a white paper label with the text U F 105636. The perimeter is scalloped.

- Panels 3 and 4 (Top-Right): Two lateral views showing the low, rounded profile of the test and the vertical distribution of the tubercles. A white scale bar representing 10 mm is positioned below panel 1.

Bottom row (Specimen U F 14131):

- Panel 5 (Bottom-Left): Apical view of a lighter-colored specimen, showing similar pentameral symmetry and tuberculation.

- Panel 6 (Bottom-Center): Oral view showing a central depression with the handwritten identifier U F 14131.

- Panels 7 and 8 (Bottom-Right): Two lateral views illustrating the hemispherical shape and the rows of primary and secondary tubercles. A second white scale bar representing 10 mm is positioned below panel 5.

Reference Cooke1941 Arbacia waccamaw Cooke, p. 10, pl. 1, figs. 1–3.

Holotype

USNM PAL 498888 (Fig. 11). Specimen almost complete, preserved without spines. TD = 32 mm; TH = 17 mm.

Emended diagnosis

Arbacia in which ocular plates have one large tubercle, even in large specimens (TD = 40 mm); ambulacral and interambulacral tubercles largest at ambitus, much smaller aborally; interradial interambulacral tubercles present at ambitus only, on no more than two plates aborally; ambulacral tubercles irregularly developed aborally.

Occurrence

Known from North and South Carolina, and Florida. Type material is from the Intracoastal Waterway canal, 4.5 mi (7.2 km) southwest of Little River, Horry County, South Carolina, USA (USNM station 13377). Type material from the Lower Pleistocene Waccamaw Formation of South Carolina (Horry County, type locality). This species is also known from the Waccamaw Formation of North Carolina (Brunswick and Columbus counties) and the uppermost UGCLS of South Carolina. This species is here recognized for the first time in the Lower Pleistocene Caloosahatchee Formation of Florida (Hendry County; Fig. 13).

Description

Remarks

Comparison with other species of Arbacia

This species differs from all other Arbacia spp., except for A. rivuli and A. improcera, by the presence of large tubercles on the ocular plates in large, adult specimens. It differs from A. rivuli in having a higher number of interambulacral plates and in lacking a second column of interambulacral tubercles close to the interradial suture aborally. It differs from A. improcera in having a lower number of interambulacral plates, longer tags, and in lacking tubercles on the genital plates.

Arbacia percaribbeana new species

Figures 14–17

Figure 14.

Arbacia percaribbeana n. sp., holotype, UF 353522, Upper Pliocene Tamiami Formation, Quality Materials Quarry, Placida, Charlotte County, Florida, USA: (1) apical view; (2) oral view; (3) lateral view; (4) detail of interambulacrum; (5) detail of ambulacrum; (6) apical system. Scale bar = 10 mm (1–3); 5 mm (4–6).

Figure 14. Long description

A multi-panel photo containing six numbered views of a fossilized sea urchin.

Panel 1 shows the apical view, a circular top-down perspective. At the center is a small circular opening surrounded by five radiating ambulacral segments and five wider interambulacral segments with a granular texture.

Panel 2 shows the oral view, the underside of the specimen. It features a large, recessed central opening with a jagged perimeter, surrounded by a heavily tuberculated surface.

Panel 3 shows the lateral view, a side profile of the dome-shaped test. The base is flat with rounded protrusions, and the surface curves upward to a peak, showing vertical suture lines.

Panel 4 is a close-up detail of the interambulacrum, highlighting the hexagonal plates and the zig-zagging suture line running vertically through the center.

Panel 5 is a close-up detail of the ambulacrum, showing rows of small pores and larger rounded tubercles arranged in vertical columns.

Panel 6 provides a high-magnification view of the apical system, focusing on the central opening and the surrounding genital plates and pore structures.

White scale bars are present below panels 2 and 4, and to the right of panel 6, representing 10 millimeters for panels 1 through 3 and 5 millimeters for panels 4 through 6.

Figure 15.

Arbacia percaribbeana n. sp., details of test plating: (1) USNM PAL VGO-13, apical system; (2, 3) UCMP 38200: (2) aboral plates of interambulacrum; (3) aboral plates of ambulacrum. Scale bars = 10 mm (3); 5 mm (1, 2).

Figure 15. Long description

A multi-panel figure containing three numbered line drawings.

Panel 1 shows the apical system of U S N M P A L V G O-13. At the center is a large, dark, irregular circular opening. Surrounding this center are five large, interlocking plates. Each plate contains a single small, dark circular pore. A scale bar at the bottom right represents 5 mm.

Panel 2 shows the aboral plates of the interambulacrum of U C M P 38200. It depicts a tapered, vertical column of interlocking hexagonal plates. The plates are arranged in two columns meeting at a central vertical zigzag suture. Large circular primary tubercle scars are located on the outer edges of the lower plates, while smaller granules are scattered near the sutures. A scale bar at the bottom right represents 5 mm.

Panel 3 shows the aboral plates of the ambulacrum of U C M P 38200. It features a vertical arrangement of irregular plates. On the left side, there is a vertical series of paired, dark oval pore pairs. On the right side, larger circular tubercle scars are visible. The plates have a mottled appearance with varying shades of gray. A scale bar at the bottom right represents 10 mm.

Figure 16.

Arbacia percaribbeana n. sp., paratype, UF 356363, Upper Pliocene Tamiami Formation, Quality Materials Quarry, Placida, Charlotte County, Florida, USA: (1) apical view; (2–5) oblique views. Scale bars = 10 mm.

Figure 16. Long description

A multi-panel photo series of a fossilized sea urchin paratype.

Panel 1 at the top-left shows a top-down apical view. The circular test is light tan and covered in small tubercles. A dark, irregular opening is at the center. Numerous cylindrical spines radiate outward from the perimeter of the test, partially embedded in a sandy matrix. A white 10 mm scale bar is in the bottom-right corner.

Panel 2 at the top-right provides an oblique view from above. The test appears dome-shaped, rising from the matrix. Spines are seen projecting downward and outward from the sides of the dome. A white 10 mm scale bar is in the bottom-right corner.

Panels 3, 4, and 5 at the bottom show close-up oblique views of the test surface and spine attachments.

* Panel 3 focuses on the granular texture of the plates and the base of several thick, vertical spines.

* Panel 4 shows the apical opening at the top of the dome with plates radiating downward toward the spines.

* Panel 5 highlights the density of the spines as they emerge from the lower portion of the test.

Each of these three bottom panels includes a vertical white 10 mm scale bar on the right side.

Figure 17.

Morphology of Arbacia percaribbeana n. sp.: (1) USNM PAL 805806, apical view; (2) USNM PAL 805807, oblique view; (3) UF 168836, paratype, lateral view; (4–7) UF 230367, paratype: (4) apical view; (5) oral view; (6, 7) lateral views; (8) UF 232264, paratype, oblique view; (9) NHMUK E 82828-9, oblique view; (10) USNM PAL 805815, oblique view. Scale bars = 10 mm.

Figure 17. Long description

A collection of ten high-resolution photographs of fossilized sea urchins against a black background. Each panel contains a white scale bar representing 10 mm.

* Panel 1: Top-left. Apical view of specimen U S N M P A L 805806, showing a circular, flattened test with five radiating ambulacral segments and a central opening.

* Panel 2: Top-center. Oblique view of specimen U S N M P A L 805807, highlighting the domed shape and rows of small tubercles.

* Panel 3: Top-right. Lateral view of specimen U F 168836, showing the low-profile, hemispherical side view.

* Panel 4: Middle-left. Apical view of specimen U F 230367, showing clear pentameral symmetry and distinct plates.

* Panel 5: Middle-center. Oral view of specimen U F 230367, featuring a paper label with the specimen number near the central peristome.

* Panels 6 and 7: Middle-right. Two lateral views of specimen U F 230367, showing the distribution of primary and secondary tubercles along the sides.

* Panel 8: Bottom-left. Oblique view of specimen U F 232264, showing the transition from the apical surface to the lateral margin.

* Panel 9: Bottom-center. Oblique view of specimen N H M U K E 82828-9, showing a slightly weathered surface with visible plate boundaries.

* Panel 10: Bottom-right. Oblique view of specimen U S N M P A L 805815, showing the apical system and the fine texture of the ambulacral and interambulacral areas.

Reference Linder, Durham and Orr1988 Arbacia sp. indet. Linder et al., p. 8, table 1.

Type specimens

UF 353522 (Fig. 14). The holotype was collected from a weakly indurated series of pale to dark gray sandy calcarenite of the Tamiami Formation in the Quality Material Quarry in Charlotte County, Florida, USA. Specimen complete (TD = 30 mm; TH = 13 mm). Paratypes are UF 168836, 230081, 230367, 232264, and 356363.

Referred specimens

More than 35 complete tests from Florida, 25 from Venezuela and the Lesser Antilles. A complete list of referred material is available in Supplementary Data 1.

Diagnosis

Arbacia with very small ambulacral tubercles aborally; to four interambulacral primary tubercles at ambitus; inner interambulacral tubercles decreasing in size toward interradius at ambitus and positioned close to adoral plate margin.

Occurrence

Known from Florida (USA), Curaçao, Trinidad and Tobago, and Venezuela (Falcón State and Cubagua). Cocuiza Member, San Gregorio Formation, Early Pleistocene of Falcón State, Venezuela; Springvale Formation, Middle Pliocene (Piacenzian) of Trinidad; Balanus Bed (Bed 2) of the Rockly Bay Formation, Middle Pliocene of Tobago; Savarese Unit D, Seroe Domi Formation, Pliocene of Curaçao; Tamiami Formation, Late Pliocene of Florida, USA.

Description

Etymology

The species name is derived from the distribution of the species across the Caribbean region, including Venezuela and Florida.

Remarks