Paleozoic Vertebrates Research Articles

Some vertebrate types (Chondrichthyes, Actinopterygii, Sarcopterygii, and Tetrapoda) from two Paleozoic Lagerstätten of Ohio, U.S.A.

ABSTRACT The type specimens of eight Paleozoic vertebrate species from Ohio, U.S.A., originally described by J. S. Newberry and subsequently reposited in the Orton Geological Museum, are reviewed and illustrated photographically. They include four actinopterygian fish species from the Linton Konservat-Lagerstätte (Upper Freeport Coal; Carboniferous) in Jefferson County, Ohio, described in 1857 under the basionyms Mecolepis corrugatus (now Haplolepis corrugata), M. insculptus (synonymized as Parahaplolepis tuberculata), M. lineatus (now Pyritocephalus lineatus), and M. ovoideus (now Microhaplolepis ovoidea). One actinopterygian species, Eurylepis striolatus, a junior synonym of Haplolepis corrugata, was described in 1873 from the Linton deposit; and one chondrichthyan species, Orthacanthus gracilis, now replaced as Orthacanthus adamas Babcock, 2024, was first described by Newberry in 1875 from Linton. Lectotypes are designated from the syntypic series of M. insculptus and O. adamas. A tooth from the Linton Lagerstätte, originally described as a fish in 1857 under the basionym Rhizodus lancifer, is the holotype of the tetrapod (anthracosaur) Anthracosaurus lancifer. One Devonian sarcopterygian fish species, Onychodus ortoni, was described in 1889 from the Ohio Shale, Huron Shale Member, a Konservat-Lagerstätte occurring in Franklin County, Ohio.

Feeding in the Devonian antiarch placoderm fishes: a study based upon morphofunctional analysis of jaws

AbstractAntiarch placoderm fishes were an abundant component of the Middle Paleozoic vertebrate assemblages. Despite a large number of known taxa and specimens, the morphology and function of the skeletal elements of their jaws is inadequately known. Because of this, questions regarding their feeding modes and their roles in the trophic webs remain open. We present a skeletomuscular model of the antiarch jaw apparatus with an attempt to reconstruct its potential biomechanical function. The position of the upper jaw suborbital bones within the plane of the ventral side of the fish armor is suggested to represent the natural “mouth closed” position. During mouth opening, the suborbitals rotated rostrally with simultaneous depression and inward rotation of the infragnathals. The ball-and-socket jaw articulation might ensure this combined movement. Recently described lower jaw elements ofLivnolepis zadonica(Obrucheva, 1983) andBothriolepissp. from the Upper Devonian (lower Famennian) of Central Russia demonstrating very deep and porous blades of the oral division of the infragnathals queried the structure of these bones in other antiarchs. Observed porosity reflects intense vascularization to supply blood to a connective tissue underlying a supposed keratinous sheath, which protected and strengthened the jaws, as well as made possible scraping tough food objects, such as thallus algae, from the substrate.Having evolved during the Silurian in the Pan-Cathaysian zoogeographical province, antiarchs migrated to Gondwana during the Emsian and later to Euramerica during the Eifelian. Supposedly, antiarchs became the first macrophytophagous vertebrates occupying the trophic level of primary consumers during the late Silurian–Early Devonian. This event diversified the only previously existing predator–prey interrelationships between filter-feeding agnathans and predatory gnathostomes.

The Early Permian Bolosaurid Eudibamus cursoris: Earliest Reptile to Combine Parasagittal Stride and Digitigrade Posture During Quadrupedal and Bipedal Locomotion

A comprehensive description of the holotype skeleton is presented here for the first time of the lower Permian (Artinskian) reptile Eudibamus cursoris from the Bromacker locality of Germany since the brief description of the holotype in 2000. The holotype is essentially complete and is the only known bolosaurid represented by a well-preserved articulated skeleton. Included in the description here is a superbly preserved, partial, articulated second specimen of E. cursoris discovered at the same locality that includes a short portion of the vertebral column associated with the pelvis and right hindlimb. Descriptions of the holotype and new specimen add substantially to features of the skull and postcranium that not only confirm a bolosaurid assignment, but also add significantly to an already long list of structural features supporting an ability unique among Paleozoic vertebrates to reach relatively high bipedal and quadrupedal running speeds employing a parasagittal stride and digitigrade stance with the limbs held in a near vertical posture. Structural differences between the two specimens are restricted to the tarsi and are attributed to different ontogenetic stages of ossification, with the holotype representing a more juvenile individual, and the larger second specimen representing a more mature animal.

First occurrence of fossil vertebrates from the Carboniferous of Colombia

Data concerning Paleozoic vertebrates from the South American continent are still scarce. In Colombia, occurrences were until now restricted to the Late Devonian fish assemblage from Floresta and, ...

A new reptile from the Richards Spur locality, Oklahoma, U.S.A., and patterns of Early Permian parareptile diversification

ABSTRACTThe Lower Permian Richards Spur locality is the most speciose Paleozoic continental vertebrate assemblage currently known, and a significant proportion of the tetrapod diversity found at the locality is made up of parareptiles. The first Richards Spur parareptile to be described was Colobomycter pholeter. It has been characterized by its enlarged premaxillary tooth and paired enlarged maxillary teeth, unique dentition that grants it an appearance quite distinct from other parareptiles at Richards Spur. Here we describe new cranial material from Richards Spur that is referable to Colobomycter. This new material differs from that of C. pholeter in that it possesses at least three more teeth on its maxilla, the enlarged premaxillary and maxillary teeth are more gracile than those in C. pholeter, and the lacrimal is restricted externally to the orbital margin and does not exhibit an extra lateral exposure. We infer that these differences merit specific distinction and assign the new fossil to Colobomycter vaughni, sp. nov. The discovery of C. vaughni at Richards Spur is important, because it reveals the presence of another member of the clade Lanthanosuchoidea in Oklahoma, making it the sixth to be found in the state. The large number of taxa from this clade found in Oklahoma suggests that during the Early Permian, this area of western Laurasia was the center of a radiation of small, predatory lanthanosuchoids.http://zoobank.org/urn:lsid:zoobank.org:pub:149450CF-4CB8-4099-B037-7E371A5AB286SUPPLEMENTAL DATA—Supplemental materials are available for this article for free at www.tandfonline.com/UJVPCitation for this article: MacDougall, M. J., S. P. Modesto, and R. R. Reisz. 2016. A new reptile from the Richards Spur locality, Oklahoma, U.S.A., and patterns of Early Permian parareptile diversification. Journal of Vertebrate Paleontology. DOI: 10.1080/02724634.2016.1179641.

Paleogeographical and paleoecological constraints on paleozoic vertebrates (chondrichthyans and placoderms) in the Ardenne Massif: Shark radiations in the Famennian on both sides of the Palaeotethys

Three chondrichthyan radiations are registered in the Famennian of the Ardenne Massif (Belgium). These radiations are already observed in Morocco and in the Carnic Alps, their acme being related with the early expansa transgression. Comparisons of univariate statistical descriptors like Margalef richness and Shannon–Wiener diversity index show variations between both margins of the Paleotethys, variations interpreted in terms of trophic relationships. The Ardenne area, a northern shallow carbonate platform is characterized during the Famennian by endemic shark taxa with durophagous dentition. The southern open deep-sea area, the Variscan Sea, contains large placoderms probably disclosing a negative feedback on “cladodont” chondrichthyans. This supports the hypothesis that the Armorica platelet behaved like a barrier between the central southern Laurussia and northern Gondwana.

First vertebrate body remains from the Permian of Argentina (Elasmobranchii and Actinopterygii)

Isolated shark and actinopterygian teeth and scales were found in marine levels of the El Jarillal Formation (Early Permian), which crops out near the Cerro Vizcacha, Provincia de Mendoza, Argentina. Scarce previous Paleozoic vertebrate remains are known from Argentina and none was described from the Permian. Only tetrapod traces were reported before. However, vertebrates (especially fishes) are relatively abundant in other South American countries such as Brazil, Bolivia, Uruguay, Colombia, and Venezuela, from where “agnathan”, placoderm, acanthodian, chondrichthyan, actinopterygian, dipnoan, crossopterygian, and tetrapod remains are known. In this paper we report the southernmost Paleozoic vertebrates body remains record and the first description of a hybodontid tooth from the Paleozoic of South America. Hybodontiforms were previously known in South America by fin spines, placoid scales and one putative undescribed tooth. We also give the first report South American shark dermal denticles traditionally ascribed to the form genus Petrodus, which probably belongs to a hybodontoid shark. Finally, several “basal actinopterygians” scales and teeth are assigned to morphotypes found in other South American Permian Formations. We did not found other fish taxa already known from late Paleozoic beds of the continent such as xenacanthiform sharks, lungfishes or coelacanthiforms. As an appendix, we summarize the Permian fish record of the continent.

Development of the dermoskeleton in Superciliaspis gabrielsei (Agnatha: Osteostraci)

ABSTRACT Osteostracans are Paleozoic jawless vertebrates, likely the sister group to gnathostomes (jawed vertebrates). It was previously believed that the osteostracan dermoskeleton began ossification when the individual neared adult size, restricting further growth once a dermoskeletal covering was achieved. However, we describe here small, well-preserved articulated specimens of the osteostracan Superciliaspis gabrielsei. These specimens are the best-known juvenile osteostracans, and document dermoskeletal development at an evolutionary stage highly relevant to the origin of gnathostomes. Ossification began before the animal reached 20% of adult size. Bones grew by multiple means, including initiation of new bone units, marginal growth, and fusion into larger bones. In the head, paired elements were among the first to ossify. In the trunk dermoskeleton of juvenile heterostracans, bones developed first along the midline, but in Superciliaspis gabrielsei, a lateral to median polarity is seen, with ventrolateral ridge scales the first to appear.

A brief review of studies on palaeogeography of Middle Paleozoic vertebrates in China

New discoveries of Silurian and Devonian vertebrates in China and their palaeogeographical significance are reviewed. The Middle Paleozoic fish assemblages of the Tarim basin are similar to those of South China. Fossil vertebrate evidence shows the appearance of the Chinese platform in Middle Paleozoic and its close relation with East Gondwana at least in Early Devonian.

Environment of the Early Paleozoic vertebrates

A comprehensive review of the known pre-Devonian vertebrate localities suggests that the non-marine environment was not invaded until about Wenlock, early mid-Silurian time. Known, well-dated Late Cambrian, Ordovician, and Early Silurian vertebrate localities are all in the marine environment. Considerations of paleogeography for the pre-Wenlock indicate that most of the vertebrate localities are too distant from shorelines to provide any basis for transport from the non-marine environment to a marine depositional site as a favored explanation—the articulated nature of the vertebrates from some of these pre-Wenlock occurrences also supports this interpretation. Reconsideration of both the physiological and embryological evidence relative to living vertebrates, and some related chordates, is also consistent with the view that the vertebrates originated in the marine environment.

THE EVOLUTION OF AIR-BREATHING IN PALEOZOIC GNATHOSTOME FISHES.

The orthodox view of vertebrate evolution holds that air-breathing first arose in gnathostome fishes inhabiting freshwater swamps and marshes of the Paleozoic Era (Barrell, 1916; Inger, 1957; Romer, 1966, 1967; Thomson, 1969a, 1971). Paleoclimatic evidence indicates that these aquatic environments were characterized by low levels of dissolved oxygen, at least during dry seasons, owing to the combined effects of high ambient temperature, inadequate circulation of the shallow waters by wind, and high oxygen demands of microbes and decaying vegetation (Barrell, 1916; Inger, 1957; Thomson, 1969a). In such environments, the habit of air-breathing presumably was subjected to strong selection pressures (Romer 1966, 1967; Thomson, 1971), for in the absenc,e of some auxiliary respiratory mechanism permitting the exploitation of atmospheric reservoirs of oxygen, survival seems to have been unlikely (Romer, 1966). Lungs subsequently evolved in the successful inhabitants of these stagnant waters as greater and greater reliance was placed upon air-breathing to provide the oxygen necessary to support metabolism. The strongest support for the aforementioned theory comes from consideration of the distribution of contemporary airbreathing fishes. T'hese fishes reach their highest diversity in warm, shallow inland waters of the tropical lowlands (Carter, 1957; Johansen, 1970), where hypoxic conditions commonly occur (Carter and Beadle, 1931; Willmner, 1934). Since the success of these swamp-dwelling fishes is related to their ability to tap atmospheric supplies of oxygen, it seems reasonable to conclude that comparable environmental conditions during the Paleozoic must have led to the evolution of air-breathing among ancient fishes (Carter and Beadle, 1931). Moreover, the air-breathing habit is quite uncommon among contemporary fishes inhabiting, marine or estuarine environments (Carter, 1957; Johansen, 1970). Since seawater generally is well circulated and fully aerated it is regarded as unlikely that Paleozoic fishes inhabiting this medium, like Recent fishes, could have met with difficulty in satisfying their needs for oxygen (Carter, 1957; Johansen, 1970). The theory for a freshwater origin of air-breathing (and lungs) in Paleozoic vertebrates has won wide acceptance; and the pervasiveness of the theory is revealed by the fact that certain groups of vertebrates are regarded as having originated in freshwaters, despite the existence of paleontologic evidence to the contrary, largely because they possess lungs (Thomson, 1969a,b). My objective is to show that necessary conditions for the evolution of air-breathing could have existed during the Paleozoic Era in certain marine or estuarine situations; and in this way I hope to provide for a re-interpretation of many of the paleontologic data.

An Ophiacodont Reptile from the Permian of Kansas

A specimen of ophiacodont reptile (Winfieldia hilli, gen. et sp. nov.) is described from the Permian Fort Riley limestone of Kansas. Its morphology, its deposition in a marine formation, and the stratigraphy of Paleozoic vertebrate remains from the Northern Plains are discussed.

The Primitive Structure of the Mandible in Amphibians and Reptiles

There has been much uncertainty and doubt as to the structure of the mandible in the early amphibians and reptiles. The abundant material of paleozoic vertebrates in the University of Chicago museum has enabled me to determine beyond reasonable doubt, not only the intimate structure of the pelycosaurian and cotylosaurian mandibles, but also that of a very typical temnospondylous stegocephalian. A full discussion with figures of the various forms in which I have determined the structure will be published in a more extensive work on Permian vertebrates next June. For the present I give only the more essential, newly discovered characters in the cotylosaurian genus Labidosaurus and the stegocephalian Trimerorhachis, accompanied by figures of the latter. A brief description of the structure in Dimetrodon has already been published by me in Science. The coronoid of Labidosaurus extends from about the seventh tooth along the alveolar margin to about one inch back of the teeth, appearing on the inner side of the outer wall of the meckelian orifice as a narrow, thin bone. The bone forms the anterior wall of the orifice, joining the prearticular much as it joins the angular in the alligator. The prearticular covers the inner side of the mandible posteriorly much as in Trimerorhachis, though not so broadly, and extends forward below the coronoid to about opposite the anterior end of the inframeckelian foramen, where it joins the splenial. The splenial, as usual, enters into the symphysis anteriorly and extends back to the inframeckelian orifice about opposite the last tooth, and forms also part of the inferior margin of that foramen; it is only narrowly visible on the outer side of the mandible.