Non-technical Summary
Glassiids are a group of smooth-shelled, rather unattractive Silurian and Devonian brachiopods that have barrel-shaped inner spiralia that lie across the valves. Few genera in the family have known spiralia. This contribution tries to amend that by looking at the internals of two of the five genera attributed to the family. One, the genus Trigonatrypa, has spiralia like the rest of the family. The other, Karbous, has spiralia directed down into the dorsal valve. This new observation based on similar internal characteristics of the type species Karbous aperinus relocates the genus to the family Karpinskiidae.
Introduction
The superfamily Glassioidea appeared in the Wenlock with the common species Glassia Davidson, Reference Davidson1881. Three more genera appeared in Devonian but never became widespread (Copper, Reference Copper1986, Reference Copper, Williams, Brunton and Carlson2002). The genera in the superfamily have barrel-shaped and medially directed spiralia, with the narrowest end pointing toward the jugal processes (Copper, Reference Copper, Williams, Brunton and Carlson2002). The earliest spire bearers also have medially directed spiralia but with their apices oriented laterally. Glassiides exhibit separate jugal processes, often with well-developed jugal plates as opposed to the jugum in the earliest atrypides. Of the five genera discussed in the Treatise on Invertebrate Paleontology (Copper, Reference Copper, Williams, Brunton and Carlson2002), only Glassia and Peratos Copper, Reference Copper1986 possess known spiralia; thus, it is difficult to assign the remaining genera to the group with certainty. Karbous Havlíček, Reference Havlíček1985 was classified as a glassiide by Copper (Reference Copper, Williams, Brunton and Carlson2002). Under doubt, Trigonatrypa Havlíček, Reference Havlíček, Havlíček and Kukal1990 was classified as a glassiide, but Copper (Reference Copper, Williams, Brunton and Carlson2002) stated that assignment to Lissatrypidina or Atrypidina was possible and that the brachiopod might even represent a rhynchonellide. The thick shell walls and the large dental cavities justified placing it among the glassiides. This paper aims to show what kind of spiralia Karbous and Trigonatrypa exhibit.
Geological setting
The upper Emsian and the Eifelian in the Prague Basin of Central Bohemia, Czech Republic, are represented by the Daleje-Třebotov and the Choteč formations, respectively. The boundary between the Lower and Middle Devonian lies in the upper part of the Třebotov Limestone, composed of light gray and red-colored, well-bedded, micritic to biomicritic limestones (Chlupáč, Reference Chlupáč, Chlupáč, Havlíček, Kříž, Kukal and Štorch1998). The Choteč Formation is mainly represented by the Choteč Limestone, consisting of dark gray, well-bedded, micritic limestones with redeposited bioclastic material. The Třebotov and Choteč limestones occupy most of the Upper Emsian to the Eifelian infill of the Prague Basin. However, a small area near Koněprusy has a different facies development. The variable bathymetric water marine conditions and the Emsian and Eifelian global greenhouse setting (Copper, Reference Copper, Brunton, Cocks and Long2001) facilitated reef environments through the Pragian Stage with a break in the Lower Emsian and from the Upper Emsian to the beginning of the Givetian. The Upper Emsian is represented by the mostly pinkish-gray crinoidal Suchomasty Limestone, which is graded to the light-gray Acanthopyge Limestone of Eifelian age. Both units are rich in diverse, shallow-water brachiopods, corals, and trilobites reviewed by Chlupáč (Reference Chlupáč, Chlupáč, Havlíček, Kříž, Kukal and Štorch1998). The different limestone lithologies enable (with some caution) the distinction of the stratigraphic level of fossils in old collections.
The Koněprusy area has been a source of extensive fossil material since the mid-nineteenth century. Unfortunately, the older collections, including collections of the brachiopod types of J. Barrande (Barrande, Reference Barrande1847, Reference Barrande1879), are labeled only Konieprus (Koněprusy). His collections of mixed fossils were collected in limestone from a small area at Zlatý Kůň, where numerous small quarries were situated in the nineteenth and twentieth centuries. This is the same area where most of the materials described by Barrande (Reference Barrande1847, Reference Barrande1879), Siehl (Reference Siehl1962), Havlíček (Reference Havlíček1956, Reference Havlíček1959, Reference Havlíček1967, Reference Havlíček1982, Reference Havlíček1987), and Havlíček and Vaněk (Reference Havlíček and Vaněk1996, Reference Havlíček and Vaněk1998) were collected.
Materials and methods
The type locality of Karbous aperinus Havlíček, Reference Havlíček1985 is the small abandoned Herget’s Quarry on the southeastern slope of the Zlatý Kůň hill (Havlíček and Kukal, Reference Havlíček and Kukal1990) near Koněprusy, Czech Republic, 49°54’57.246”N, 14°04’12.182”E. We acquired topotype material of K. aperinus.
We could not obtain material of the type species Trigonatrypa holynensis Havlíček, Reference Havlíček, Havlíček and Kukal1990, because the locality has not been accessible for collection for > 50 years. Moreover, the preservation mode in heavily weathered soft limestone residuum would not enable the serial sectioning of shells from this locality. Comparisons of the types are based on the topotypes for Karbous and descriptions by Havlíček (Reference Havlíček, Havlíček and Kukal1990) of the type material of T. holynensis. We sectioned a closely related species, T. baucis (Barrande, Reference Barrande1847), and topotypic material for K. aperinus and K. hassiacus (Siehl, Reference Siehl1962).
The new Karbous hassiacus and Trigonatrypa baucis material was obtained from the Choteč Formation, Acanthopyge Limestone (Eifelian). Vladimír Havlíček and the second author sampled it exclusively in a small area near the road from Koněprusy to Suchomasty, 49°54’50.203”N, 14°4’30.080”E (in abandoned quarries and the nearby field; localities 10 and 11 of Havlíček and Kukal, Reference Havlíček and Kukal1990). Ten meter thick, poorly-bedded crinoid, coral, and brachiopod gray limestones, formerly labeled the Amplexus Limestone, belong to the Tortodus kockelianus australis and T. kockelianus kockelianus biozones interval (Vodrážková and Suttner, Reference Vodrážková and Suttner2020).
The material is plentiful but challenging for serial sections because most shells are either filled with secondary calcite or have geopetal filling with some micritic material. Spiralia are shown as ghosts within the secondary calcite in the actual specimens, and they generally cannot be discerned in the peels. The whole shells were encased in epoxy with the beak vertically up. The specimens were small, so that we could section three specimens simultaneously for each species. The epoxy stubs were then ground down, and acetate peels were taken at 0.1–0.2 mm intervals near the posterior end and 0.3 mm intervals farther anteriorly.
Repositories and institutional abbreviations
Specimens examined in this contribution are deposited in the Paleontological Collections (PMO) of the Natural History Museum, University of Oslo, Norway. Type material for the species described is deposited at the National Museum of Prague (L); Museum of Dr. Bohuslav Horák in Rokycany (VH), Czech Republic; and Bonn Institute for Organismic Biology, Section 5, Palaeontology und Goldfuß-Museum (BIOB-PAL), Germany.
Systematic paleontology
Order Atrypida Rzhonsnitskaia, Reference Rzhonsnitskaia and Sarytcheva1960
Suborder Davidsonioidea Copper, Reference Copper1996
Superfamily Palaferelloidea Spriestersbach, Reference Spriestersbach1942
Family Karpinskiidae Poulsen, Reference Poulsen1943
Subfamily Karpinskiinae Poulsen, Reference Poulsen1943
Genus Karbous Havlíček, Reference Havlíček1985
Type species
Karbous aperinus Havlíček, Reference Havlíček1985, Daleje-Třebotov Formation, Suchomasty Limestone (Emsian), Koněprusy, Herget’s Quarry, Czech Republic.
Karbous aperinus Havlíček, Reference Havlíček1985
Figures 1.1–1.7, 2, 3
(1–7) Karbous aperinus Havlíček, Reference Havlíček1985, Suchomasty Limestone (Upper Emsian to the Eifelian), Herget’s Quarry, Koněprusy, Central Bohemia, Czech Republic: (1–4) holotype, VH 4949a, dorsal (1), ventral (2), anterior (3), and lateral (4) views of shell; (5–7) paratype, VH 4949b, dorsal (5), ventral (6), and lateral (7) views of shell. (8–12) Karbous hassiacus (Siehl, Reference Siehl1962), PMO 251.391, Choteč Formation (Eifelian), Acanthopyge Limestone, Koněprusy, Central Bohemia, Czech Republic, dorsal (8), ventral (9), lateral (10), posterior (11), and anterior (12) views of shell. (13–17) Trigonatrypa baucis (Barrande, Reference Barrande1847), PMO 251.393, Choteč Formation (Eifelian), Acanthopyge Limestone, Koněprusy, Central Bohemia, Czech Republic, brachial (13), pedicle (14), anterior (15), lateral (16), and posterior (17) views of shell.
Karbous aperinus Havlíček, Reference Havlíček1985, Suchomasty Limestone, (Upper Emsian to the Eifelian), Herget’s Quarry, Koněprusy, Central Bohemia, Czech Republic, sketches of serial sections: (1) PMO 252.051a; (2) PMO 252.051b. Distance from the ventral umbo indicated in mm for each section. Ventral valve positioned upward.
Karbous aperinus Havlíček, Reference Havlíček1985, Suchomasty Limestone, (Upper Emsian to the Eifelian), Herget’s Quarry, Koněprusy, Central Bohemia, Czech Republic, PMO 252.051a (1) and 252.051b (2), polished sections with spiralia.
Reference Barrande1879 Atrypa philomela Barrande, pl. 134, case 1, fig. 5, pl. 146, case 2, figs. 1, 2, 5.
Reference Havlíček1985 Karbous aperinus Havlíček, p. 236, pl. 1, fig. 3, pl. 2, figs. 1, 2, text-figs. 2, 3.
Reference Havlíček, Havlíček and Kukal1990 Karbous aperinus; Havlíček, pl. 9, figs. 3–6, text-fig. 20.
Holotype
VH 4949a, Daleje-Třebotov Formation, Suchomasty Limestone (Upper Emsian to Eifelian), Hergetʼs Quarry, Zlatý Kůň hill, Koněprusy, Central Bohemia, Czech Republic.
Material
PMO 252.051a–c, sectioned whole specimens; PMO 252.051d–I, whole shells, all from the Daleje-Třebotov Formation, Suchomasty Limestone (Upper Emsian to Eifelian), Herget’s Quarry, Koněprusy, Central Bohemia, Czech Republic.
Description
Based on nine small topotypic specimens.
External characters
Small to medium (average length 9 mm) rounded shell, slightly longer than wide, with a high pedicle valve relative to the brachial valve (Fig. 1.1 –1.7). Depth an average of 55% of length. Strong beak overhanging the hinge line (Fig. 1.4, 1.7). Shell smooth with a few growth lines anteriorly. Weakly uniplicate anterior margin and maximum width at midlength. Interarea hypercline to anacline with a small, elongated apical foramen and small deltidial plates (Fig. 1.5).
Internal characters
Very thick shell wall posteriorly without any median ridge in the brachial valve. Teeth with small dental cavities (Fig. 2.1, 2.2), curving below delicate socket plates resting on a thick pad. Thin crura and thick jugal processes possibly terminating in large jugal plates. Spiralia with five whorls, best viewed in the polished cross sections of the specimens (Fig. 3.1, 3.2). The immature shell (Fig. 3.2) has spiralia directed mediodorsally. The mature valve has one spiralium directed dorsally; the other spiralium is deformed.
Remarks
All specimens of Karbous aperinus come from white crinoidal limestone in a small, abandoned quarry on the southeastern slope of Zlatý kůň hill. The associated fauna includes more brachiopod species, mostly costate rhynchonellid brachiopods (see Havlíček and Kukal Reference Havlíček and Kukal1990), which are known only from this locality. Currently, the locality is inside an area protected by State Law and new sampling is impossible without permission.
Karbous hassiacus (Siehl, Reference Siehl1962)
Karbous hassiacus (Siehl, Reference Siehl1962), PMO 251.39, Choteč Formation (Eifelian), Acanthopyge Limestone, Koněprusy, Central Bohemia, Czech Republic, sketches of serial sections. Distance from the ventral umbo indicated in mm for each section. Ventral valve positioned upward.
Reference Siehl1962 ?Cryptatrypa hassiaca Siehl, p. 198, pl. 27, figs. 5, 6, pl. 37, figs. 4, 6.
Reference Havlíček1985 Karbous hassiacus; Havlíček, p. 238.
Reference Copper1986 Peratos hassiacus; Copper, p. 158.
Reference Havlíček, Havlíček and Kukal1990 Karbous hassiacus; Havlíček, pl. 11, fig. 7a–d.
Holotype
Siehl BIOB-PAL-Siehl-4, Greifenstein Limestone (upper Eifelian), Hörre at Greifensteine (Nature Reserve), Rhineland, Germany.
Description
Due to the limited material and the excellent description by Siehl (Reference Siehl1962), the description given here is brief.
External characters
Small (average length 7 mm), gently ventribiconvex to biconvex shell with rounded to slightly pentagonal shell outline (Fig. 1.8–1.12). The valves are smooth, with few growth lines. The anterior commissure is rectimarginate. The shell is approximately as wide as long (96–102% w/l) and slightly more than half as deep as long. The maximum width is placed slightly anterior to midlength. The hinge line is astrophic, and the beak is medium-sized and does not curve beneath the hinge line. The interarea is anacline with a small, elongated apical foramen and prominent deltidial plates (Fig. 1.8).
Internal characters
The shell wall is thick posteriorly with no septum or median ridge in the dorsal or ventral valve. The teeth have dental cavities that are triangular to teardrop-shaped (Fig. 4). The dental plates are short and converge slightly ventrally. Anteriorly, the teeth are relatively slender and curve below thin and delicate hinge plates. The hinge plates have a flat ventral surface, are low, and are situated on the thickened valve floor. A cardinal pit is present posteriorly, but a cardinal process is missing. The crura are positioned medially in the brachial valve and can be followed a short distance anteriorly. The connection between the crura and jugal processes was not observed. However, medium-sized, relatively thin jugal plates are close together in a medioventral position. Spiralia are obscured by secondary calcite in the peel. However, the sectioned specimen has discernable spiralia directed dorsally. The observed number of whorls is four, but a slightly higher number is likely to be found with further grinding anteriorly.
Material
PMO 251.391, whole sectioned shell; PMO 251.392, whole shell; both from Choteč Formation, Acanthopyge Limestone, Eifelian, Koněprusy, Central Bohemia, Czech Republic.
Remarks
Karbous hassicus is abundant in micritic, mostly crinoidal and coral limestone at several localities in a small area between Zlatý Kůn and Kobyla hills. The species is associated with diverse smooth-shelled brachiopods (see Havlíček and Kukal, Reference Havlíček and Kukal1990), and diverse, mostly proetid trilobites. Currently, several sites are still accessible for collecting.
Superfamily Glassioidea Schuchert & LeVene, Reference Schuchert, LeVene and Pompeckj1929
Family Glassiidae Schuchert & LeVene, Reference Schuchert, LeVene and Pompeckj1929
Genus Trigonatrypa Havlíček, Reference Havlíček, Havlíček and Kukal1990
Type species
Meristella holynensis Havlíček, Reference Havlíček1956, Třebotov Limestone (Lower Eifelian), Praha-Holyně, Czech Republic.
Trigonatrypa baucis (Barrande, Reference Barrande1847)
Trigonatrypa baucis (Barrande, Reference Barrande1847), Choteč Formation (Eifelian), Acanthopyge Limestone, Koněprusy, Central Bohemia, Czech Republic, sketches of serial sections: (1) PMO 251.396; (2) PMO 252.051; (3) PMO 251.397. Distance from the ventral umbo indicated in mm for each section. Ventral valve positioned upward.
Reference Barrande1847 Terebratula baucis Barrande, p. 389, pl. 16, fig.7.
Reference Barrande1879 Merista? baucis; Barrande, pl. 17, case 4, figs. 1–11.
Reference Havlíček, Havlíček and Kukal1990 Trigonatrypa baucis; Havlíček, p. 155–157, pl. 10, fig. 2, pl. 12, fig. 5, text-figs. 17, 18.
Lectotype
L 23982, shell figured by Barrande (Reference Barrande1847, pl. 16, fig. 7a–c); refigured by Barrande (Reference Barrande1879, pl. 17, case 4, fig. 10); Acanthopyge Limestone (Eifelian), Koněprusy, Central Bohemia, Czech Republic.
Description
Havlíček (Reference Havlíček, Havlíček and Kukal1990) described the exterior of the valves in great detail.
External characters
Shell small (average length 14 mm), dorsibiconvex with a pronounced trigonal shape. The anterior margin is rectimarginate with a weak sulcus on the ventral and dorsal valves (Fig. 1.13, 1.14, 1.16). The valves are slightly longer than wide (90–94% w/l), with the maximum width near the anterior margin. The hinge line is astrophic, and the beak is medium to large with an anacline interarea. The foramen is tiny and situated apically, and the deltidial plates are well developed.
Internal characters
Internal descriptions are based on serial sections of seven shells. The shell wall is thick with a short median ridge. Small and large shells exhibit slightly different internal configurations, as depicted in Figures 5.1–5.3. Figure 5.1 shows the hinge plates resting on the bottom of the valve. There is an initial shift toward the side seen in Figure 5.2, and farther migration was documented by Havlíček (Reference Havlíček, Havlíček and Kukal1990, figs. 17, 10.2). Figure 5.3 depicts hinge plates on the side wall in the largest shell with the deepest brachial valves.
All variations showcase medium to stout teeth and large but narrow dental cavities with relatively short dental plates. The hinge plates, delicate with a flat upper surface, are either sitting on a low platform or fastened to the wall, with variations depending on the depth of the brachial valve. A cardinal pit can be present. The crura jut out medioanteriorly and are solid. The jugal processes are distinct and positioned posteroventrally. The jugal plates are thin and oriented laterally. The spiralia are discerned as a sideways-lying figure eight; thus, they are medially directed. The exact number of whorls is difficult to ascertain but is between four and six.
Material
PMO 251.393–251.395, whole shell; PMO 251.396–251.397, 252.052; sectioned whole shells; all from Choteč Formation, Acanthopyge Limestone, Koněprusy, Central Bohemia, Czech Republic.
Remarks
The species frequently occurs together with shells of Karbous hassiacus at several localities in a small area between Zlatý Kůň and Kobyla hills. This is the source area of almost all new material. However, the types of Barrande were likely sampled near the summit of Zlatý Kůň hill, where small exposures of the Acanthopyge Limestone were recently located inside the protected area. The species was also newly observed in rocks from temporary excavations (in 2022) inside the protected area, likely near Barrandeʼs original type locality.
Results
Peels made of topotype material of the type species Karbous aperinus collected in Herget’s Quarry closely resemble the material described by Havlíček (Reference Havlíček1985). Despite poor preservation, crura, jugal processes, and spiralia can be discerned in the combined cross sections of the topotypes. Calcite crystals obscure the presence of jugal plates, but the plates are most likely large. Most importantly, the spiralia have a dorsal orientation in mature valves, whereas juvenile valves display a mediodorsal direction.
Karbous hassiacus from Koněprusy shows a mix of characteristics between Peratos and Karbous type species. It has the elongated foramen found in K. aperinus and the prominent deltidial plates of P. arretus Copper, Reference Copper1986. Karbous hassiacus has dorsally directed spiralia, further separating K. hassiacus from Peratos with its medially directed spiralia. The type species, K. aperinus, is similar in shape to K. hassiacus, but a more erect beak and large deltidial plates in K. hassiacus distinguish the two. Internally, they are close.
Peels of the species Trigonatrypa baucis from Koněprusy reveal medially directed spiralia. There is an ontogenetic development from shallower to deeper valves. A gradual reorientation of hinge plates follows. The type species, T. holynensis, differs from T. baucis in shape. The latter is triangular, with evenly sloping lateral margins from the beak. The type species broadens rapidly near the posterior margin and then slopes gently posteriorly. In cross section, the valve of T. baucis is more evenly rounded than that of the type species. Also, T. holynensis has a strongly incurved beak resting on the brachial beak compared with a more erect beak in T. baucis. The smooth shell and broadly triangular shape with a maximum width close to the rectimarginate anterior unite these species. The internal features of T. holynensis are poorly known but share a thick shell wall with T. baucis.
Most materials display geopetal infill, and the secondary calcite obscures some structures. None of the sectioned specimens shows a connection between the crura and the jugal processes, suggesting that the ends of the crura were probably feathered, as is common among glassiides.
Discussion
The species Karbous hassiacus was placed in the genus Peratos by Copper (Reference Copper1986) probably due to the prominent deltidial plates and erect beak. Havlíček (Reference Havlíček1985) and Copper (Reference Copper, Williams, Brunton and Carlson2002) defined Karbous as having minute deltidial plates. Internally, they are distinctly different, with the type species of Peratos having long, straight dental plates with sturdy teeth and hinge plates fastened to the shell wall. The type species of Karbous has small dental cavities and more delicate hinge plates sitting on a pad on the bottom of the floor. Karbous hassiacus has dorsally directed spiralia, further separating K. hassiacus from Peratos with its medially directed spiralia.
Copper (Reference Copper1986) assigned Karbous to the subfamily Glassiinae, but later dropped the subfamily and assigned it to the family Glassiidae. Glassiidae have spiralia that are barrel-shaped and medially directed as their main characteristics. Copper’s placement is surprising because Havlíček (Reference Havlíček1985) defined Karbous as having spiralia directed dorsally. Furthermore, Siehl (Reference Siehl1962) stated that his new species, Cryptatrypa hassiaca Siehl, Reference Siehl1962, possesses spiralia pointing dorsally with three to four whorls. Their findings have been corroborated here.
Havlíček (Reference Havlíček1985, Reference Havlíček, Havlíček and Kukal1990) placed Karbous in the Lissatrypidae Twenhofel, Reference Twenhofel1914. Most characters fit within this group. However, all known lissatrypids possess solid teeth and dorsomedially directed spiralia. We place the species in Karpinskiidae Poulsen, Reference Poulsen1943. Karpinskiidae shows an apsacline to orthocline area, thick shell wall, large dental cavities, delicate hinge plates, and dorsally directed cardinalia like in mature Karbous. Karpinskiidae differ in having ribs and generally being triangular. However, Eokarpinskia Rzhonsnitskaia, Reference Rzhonsnitskaia1964 has very fine ribs, giving a smooth impression (Copper, Reference Copper, Williams, Brunton and Carlson2002), and the fine-ribbed Neokarpinskia Mizens, Reference Mizens1977 has the same shape as Karbous.
Havlíček (Reference Havlíček, Havlíček and Kukal1990) stated that adult shells of Trigonatrypa baucis became relatively deeper with size. This fits with the reorientation of the hinge plates found in this study. The shape of the spiralia and position of the jugal processes leave no doubt that this species belongs to the Glassiidae. Despite the poorly known internal of T. holynensis, we assume that the type species and T. baucis belong to the same genera. Likely, both display spiralia that are mediodorsally directed. However, the few details about internal structures in the type species are insufficient for certainty.
Conclusions
Both Karbous aperinus and K. hassiacus have dorsally directed spiralia in mature specimens. The genus was placed in the Lissatrypidae by Havlíček (Reference Havlíček1985, Reference Havlíček, Havlíček and Kukal1990) and in the Glassiidae by Copper (Reference Copper, Williams, Brunton and Carlson2002). We place Karbous in the Karpinskiidae based on its interior similar to that of Karpinskiidae, with an apsacline to orthocline area, thick shell walls, dental cavities, delicate hinge plates, and dorsally directed spiralia.
Trigonatrypa is a genus tentatively placed in Glassiidae by Copper (Reference Copper, Williams, Brunton and Carlson2002). The species T. baucis has medially directed spiralia like the glassiides. Likely, the type species has the same kind of spiralia, giving credence to the placement by Copper (Reference Copper, Williams, Brunton and Carlson2002).
Acknowledgments
The second author acknowledges the institutional support (GRAK-2025-15) of the University of West Bohemia at Plzeň. The first author thanks the Geoscience Department at Williams College, Williamstown, Massachusetts for the use of their laboratory. We are also grateful for helpful reviews by A.T. Halamski at the Institute of Paleobiology, Polish Academy of Sciences, and Y. Zhang, State Key Laboratory of Paleobiology and Stratigraphy, Nanjing Institute of Geology and Palaeontology, Nanjing.
Competing interests
The authors declare none.
