Tetrapod Fossils Research Articles

Spineless displays or why inaccurate restorations of fossil invertebrates discredit our museums

Restorations of the morphology, ecology and function of fossil invertebrates may be inferior to those of groups more familiar to the public and artist, such as tetrapods. This is illustrated by an extreme example, a drawing of the Lower Jurassic pseudo- planktonic crinoid Pentacrinites Blumenbach on display in the Manchester Museum. It is shown, accurately, attached to the underside of a floating log. However, it is incorrectly illustrated attached by a cemented holdfast rather than by cirri. Indeed, the reconstruction lacks any cirri despite Pentacrinites having a dense- ly cirriferous stem; the column is too short, has an incorrect cross-section and an erroneous pattern of columnal insertion; the cup and proximal brachial plates are too big; the pattern of arm branching is wrong; and pinnulation is inaccurate. Yet Pentacrinites is known from multiple well-preserved specimens from the Jurassic of the British Isles and was originally described more than 200 years ago. Museum restorations of fossil tetrapods have to be accurate because they are a group that we know well, yet many invertebrate groups are alien to the public and, if they are 'edu cated' by such grossly inaccurate restorations, so they shall remain.

The poorly illustrated crinoid

Donovan, S.K. 2011: The poorly illustrated crinoid. Lethaia, Vol. 44, pp. 125–135. Artistic licence is kept under firm control when restoring fossil tetrapods and their natural environments, but the same care is not always applied to reconstructions of ancient invertebrates. Selected renderings of fossil crinoids illustrate grossly inaccurate skeletal geometry and outmoded ideas of palaeoautecology. Together, these combine to give the public an incorrect impression of what a fossil crinoid looked like and how it lived, in some instances inferior to what was possible in the 19th century. The reason why crinoids receive such poor service from artists is, in part, probably due to their being exotic; humans and other tetrapods are a common part of our experience, whereas stalked crinoids, although extant, can only be seen in life with the aid of a research submersible in deep water (>100 m). Crinoids also have a complex endoskeleton that requires care in illustration. They are unusual creatures in an alien environment even at the present day. But echinoderm palaeontologists need to be more energetic in promoting the correct depiction of ancient species. □Crinoidea, illustration, morphology, palaeoenvironments, reconstruction.

A new tool for determining degrees of mineralization in fossil amphibian skeletons: The example of the Late Palaeozoic branchiosaurid Apateon from the Autun Basin, France

Studying ontogenetic features of fossil tetrapods is of major interest for investigating the adaptive strategies of early tetrapods to their palaeoenvironments. To determine the degree of calcification of skeletal elements, biologists have until now relied on X-ray radiographs of organisms or isolated bones, or on thin sections. An X-ray tomographic scan of Apateon, a Carboniferous – Permian branchiosaurid from the Autun Basin, France, reveals distinct density properties related to different mineralized tissues (calcified cartilage versus bone). The rendering of Apateon as a “test individual” provides a 3D map of the degrees of ossification of the axial and cranial elements. The combination of these anatomical observations with histological information from classical thin sections made in limb bones of several other specimens of the same locality allows the detailed determination of their ontogenetic stage. A comparison with the well-known specimens of the Saar-Nahe Basin, Germany, makes it possible to investigate the influence of different palaeoenvironments on ontogenetic features.

A second specimen of Manchurochelys manchoukuoensis Endo & Shikama, 1942 (Testudines: Eucryptodira) from the Early Cretaceous Yixian Formation of western Liaoning, China

Within the Early Cretaceous Jehol Biota of China, the turtle Manchurochelys manchoukuoensis Endo & Shikama, 1942 was one of the first discovered tetrapod fossils, but no additional information on this enigmatic taxon has become available during the past half century since its discovery. Here, a new turtle skeleton from the Yixian Formation of western Liaoning Province is identified as referable to M. manchoukuoensis on the basis of an elongate oval shell, long and narrow second to fourth vertebral scutes, and two suprapygals, of which the second is much larger than the first. This specimen therefore represents the second specimen of M. manchoukuoensis, the holotype of which was probably lost during World War II. This discovery not only provides essential material that allows the validity of M. manchoukuoensis to be tested, but also substantially expands understanding of its bony anatomy, especially with regard to cranial morphology. Among other features, M. manchoukuoensis is characterized by a postorbital that does not contact the quadrate/squamosal and a deep temporal emargination, which support a close relationship with Sinemys spp. and distinguish it from the co-existing Ordosemys liaoxiensis. A cladistic analysis that includes M. manchoukuoensis further supports the hypothesis that Sinemydidae is a monophyletic group that includes Sinemys spp. and Dracochelys bicuspis.

Loss of fish actinotrichia proteins and the fin-to-limb transition

The early development of teleost paired fins is strikingly similar to that of tetrapod limb buds and is controlled by similar mechanisms. One early morphological divergence between pectoral fins and limbs is in the fate of the apical ectodermal ridge (AER), the distal epidermis that rims the bud. Whereas the AER of tetrapods regresses after specification of the skeletal progenitors, the AER of teleost fishes forms a fold that elongates. Formation of the fin fold is accompanied by the synthesis of two rows of rigid, unmineralized fibrils called actinotrichia, which keep the fold straight and guide the migration of mesenchymal cells within the fold. The actinotrichia are made of elastoidin, the components of which, apart from collagen, are unknown. Here we show that two zebrafish proteins, which we name actinodin 1 and 2 (And1 and And2), are essential structural components of elastoidin. The presence of actinodin sequences in several teleost fishes and in the elephant shark (Callorhinchus milii, which occupies a basal phylogenetic position), but not in tetrapods, suggests that these genes have been lost during tetrapod species evolution. Double gene knockdown of and1 and and2 in zebrafish embryos results in the absence of actinotrichia and impaired fin folds. Gene expression profiles in embryos lacking and1 and and2 function are consistent with pectoral fin truncation and may offer a potential explanation for the polydactyly observed in early tetrapod fossils. We propose that the loss of both actinodins and actinotrichia during evolution may have led to the loss of lepidotrichia and may have contributed to the fin-to-limb transition.

Tetrapod tracks in a marginal lacustrine setting (Middle Triassic, Argentina): Taphonomy and significance

Fossil tetrapod footprints not only provide valuable information about trackmaker paleobiology but also to give insight into details of the depositional conditions of the substrate at the time of imprinting. Therefore, in the present study the mode of formation and taphonomy of footprints in different substrates was used to investigate the gait and walking dynamics of the trackmakers as well as a source of additional information on the environmental conditions of the track-bearing beds during imprinting. The analyzed section corresponds to thick Middle Triassic lacustrine/deltaic deposits of the Ischichuca/Los Rastros Formation (Ischigualasto–Villa Unión Basin) that crops out at the Quebrada de Ischichuca in northwestern Argentina. Part of the track-bearing surfaces correspond to the top of sandy distributary channel mouth bars in a distal delta front setting that were exposed along the lake margin during a lake level fall. Cross-cutting relationships observed among ripple-marks, the footprints, and invertebrate traces of a softground suite of the Scoyenia ichnofacies suggest an omission surface. Measured trackway orientations in the sandstones are perpendicular to the paleo-shoreline, with the animals coming and going along the exposed top of the bars, probably for drinking. Laterally, the distal delta front deposits interfinger with track-bearing wackestone beds of palustrine origin deposited in a restricted local embayment lateral to the delta influenced environment. Trackway orientations in the wackestones are, in contrast, consistent with the animals moving nearly parallel to the lake border, probably along a preferred route. Evidences of a relative high groundwater table at the time of imprinting in the track-bearing surfaces are revealed by the well developed rims of extruded sediment and collapsed digits in the studied tracks and the nearly absence of associated desiccation cracks on the same surfaces. Nevertheless, temporary emergence cannot be ruled out when paleosoil formation was probably promoted as can be observed in the microstructure of both sandstones and wackestones. Moreover, footprint preservation in the wackestones might have been enhanced by partial hardening of the trampled surface during subaerial exposure. Combining ichnofossil content and taphonomy with facies analysis we identified in the lower part of the Ischichuca/Los Rastros succession a relatively rapid withdrawal of the water basinward that was probably due to a forced regression during early rifting of basin evolution. Footprints can also provide valuable information about locomotion dynamics and trackmaker behavior. Thus, the sideways deformation observed in the studied footprints, attributed to basal archosaurs and putative basal dinosaurs, can be related to an outward rotation of the foot during the step cycle, a condition that might allied to the development of the parasagittal posture in Archosauria. Besides, the densely trampled surface described herein constitutes the first documented evidence of putative social behavior among therapsid dicynodonts, the most important group of herviborous animals in the early Mesozoic terrestrial ecosystems throughout Gondwana.

The sedimentary environment of the Late Devonian East Greenland tetrapods

Abstract The Late Devonian early tetrapods in East Greenland occur in the Celsius Bjerg Group. Key occurrences are located in a detailed stratigraphic section used here to interpret the sedimentary palaeoenvironments. The palaeoenvironment for the Britta Dal Formation (which contains both Ichthyostega and Acanthostega ) is reinterpreted. The Britta Dal Formation channels have flat bases, are poorly channelized, are of low sinuosity and are part of a very major distributory system that periodically experienced extreme flooding. The tetrapod fossils were recovered from an ephemeral system that was not permanently habitable in the immediate area. Plant megafossils are poorly preserved casts and impressions dominated by lycopsids and fern-like plants. The overbank siltstones are dominated by arid soil forming processes and comprise a spectacular sequence of vertisols. The 1174 m in situ Ichthyostega locality in Paralleldal was relocated and occurs just below the midpoint of the second megacycle in the Britta Dal Formation.

Problems of correlation of South African and South American tetrapod faunas across the Permian–Triassic boundary

The best record of continental tetrapod faunas crossing the Permo–Triassic boundary (PTB) is found in the Karoo Basin of South Africa. Similar records are not known elsewhere among the former Gondwanan land masses, but it was recently proposed on the basis of palaeontological evidence that the Buena Vista Formation of Uruguay preserves a South American record of continental PTB tetrapods. The Buena Vista Formation was previously correlated to the Lower Triassic (Olenekian) Sanga do Cabral Formation of Brazil on the basis of lithostratigraphic evidence, but recent collecting in the former unit has produced a tetrapod fauna that is distinct to that documented for the latter. The unequivocal tetrapod fossils that have been described thus far from the Buena Vista Formation include indeterminate mastodonsaurid temnospondyls, a plagiosauroid temnospondyl, and a procolophonid reptile. The temnospondyls belong to Triassic groups, whereas the procolophonid is allied most closely with Early Triassic taxa from the Karoo Basin. We conclude that there is no compelling palaeontological evidence for placing any part of the Buena Vista Formation in the Permian. A precise placement of the Buena Vista Formation in the Triassic on the basis of its tetrapod fauna is not possible at this time. Accordingly, the Karoo Basin of South Africa remains the only Gondwanan basin that records a PTB tetrapod fauna.

Interpreting the autopodia of tetrapods: interphalangeal lines hinge on too many assumptions

Recently Peters proposed the concept of ‘interphalangeal lines’, defined as sub-parallel lines that could supposedly be drawn across the joints of the digits of all tetrapods. The lines were viewed as potential axes of rotation, and it was suggested that they could be used to determine the resting position of the digits, reconstruct missing digital elements of fossil tetrapods, and provide information on systematic relationships. Evidence was adduced from the skeletons of recent and fossil vertebrates and from footprints. However, detailed analysis shows that these claims are largely unfounded. Linear alignments of joints on neighbouring digits are not consistently present in tetrapods, especially across locomotor cycles. Even if present, interphalangeal (IP) lines would rarely be in an appropriate orientation to facilitate joint movements during locomotion. There is no reason to believe that IP lines would be homologous across different taxa, so they cannot be used to infer systematic relationships. Finally, the alleged support from the ichnological record is undermined by the uncertain relationship between the joint structure of the skeleton and the form of the print. We conclude that IP lines cannot be consistently constructed on tetrapod extremities, and would have minimal functional relevance or predictive power in any case.

The geological and palaeontological exploration of Laos; following in the footsteps of J. B. H. Counillon and A. Pavie

Abstract Historical studies on the exploration of SE Asia reveal interesting points concerning the geology and palaeontology of this part of the world: the first geological description of northern Laos was published in 1896 by the French geologist J. B. H. Counillon, a member of the famous Pavie Mission (1879–1895). Although scientific notes are rare in the literature about the Pavie Mission, which dealt with diplomacy and politics, Counillon's studies are very informative: they contain accurate observations on the geomorphology, hydrography, stratigraphy and palaeontology of the Mekong River and its banks. Counillon explored the dangerous region of Luang Prabang (northern Laos) with Captain Cupet. He discovered the first fossil tetrapods from Laos, and, with the help of Vasseur and Repelin, correctly referred them to dicynodont mammal-like reptiles.

Ever Since Owen: Changing Perspectives on the Early Evolution of Tetrapods

The traditional notion of a gap between fishes and amphibians has been closed by a wealth of fish-like fossil tetrapods, many discovered since the mid 1980s. This review summarizes these discoveries and explores their significance relative to changing ideas about early tetrapod phylogeny, biogeography, and ecology. Research emphasis can now shift to broader-based questions, including the whole of the early tetrapod radiation, from the divergence from other lobed-finned fishes to the origins of modern amphibians and amniotes. The fish-to-tetrapod morphological transition occurred within the Upper Devonian; the divergence of modern tetrapod groups is an Early Carboniferous event. Modern tetrapods emerged in the aftermath of one of the five major extinction episodes in the fossil record, but the earlier Devonian tetrapod radiation is not well understood. Tetrapod limbs, paired fins, and comparative developmental data are reviewed; again, research emphasis needs to change to explore the origins of tetrapod diversity.

Diictodon feliceps (Owen, 1876), a dicynodont (Therapsida, Anomodontia) species with a Pangaean distribution

ABSTRACT Dicynodont therapsids were cosmopolitan members of Middle and Late Permian terrestrial ecosystems. Despite occurring in nearly all places where tetrapod fossils of these ages are found, it is unclear whether any individual dicynodont species ever achieved a Pangaean distribution, with populations located in both Gondwana and Laurasia. Diictodon feliceps (Owen, 1876) is perhaps the best candidate for a species with such a broad distribution, but this depends on whether D. tienshanensis (Sun, 1973) from the Junggur Basin of China is a valid species. We use qualitative morphological characters, as well as linear measurement- and landmark-based morphometric techniques, to demonstrate that IVPP V.3260 (the type and only known specimen of D. tienshanensis) falls well within the range of variation displayed by D. feliceps, implying that D. tienshanensis is not a valid species. The occurrence of D. feliceps in China poses a biogeographic puzzle, since this species is otherwise known only from southern Africa. We predict that D. feliceps will be discovered in areas between southern Africa and China. However, if its absence persists in the face of continued exploration and collecting efforts, it may imply that a dispersal route and/or intervening populations of D. feliceps existed in areas in which an Upper Permian terrestrial fossil record was not preserved. Finally, if dicynodonts were adapted to exploiting components of the Gondwanan flora, the presence of D. feliceps in Gondwana and Laurasia indicates that such trophic interactions were not an insurmountable barrier to their dispersal.

Tetrapod burrows from the Triassic of Antarctica

ABSTRACT Two new tetrapod trace fossil records from the Triassic of Antarctica are described. The first is a giant terminal chamber collected from the lower Fremouw Formation (Lower Triassic) at Wahl Glacier (Beardmore Glacier region, central Transantarctic Mountains). Comparison to South African burrows known to contain the cynodont Thrinaxodon liorhinus, suggests that the Antarctic fossil was created by a tetrapod of similar size. The second set of tetrapod burrow casts was collected from Member ‘A’ of the Lashly Formation (lower Middle Triassic) and, if correctly interpreted, represent the first evidence of tetrapods from the Middle Triassic of Victoria Land. Our findings demonstrate that tetrapods were present in Victoria Land during the Middle Triassic, despite not being recovered as body fossils until the Upper Triassic in that region. Comparison to morphologically similar South African trace fossils suggests that procolophonids might have produced the Antarctic burrows, but this attribution is necessarily speculative because burrow inhabitants have not been found in situ and no morphological feature uniquely ties procolophonids to this type of trace fossil. We propose that underground burrows and dens were important shelters for Antarctic terrestrial vertebrates during the Triassic, despite a relatively moderate climate.

Osteology and taxonomic revision of Hyphalosaurus (Diapsida: Choristodera) from the Lower Cretaceous of Liaoning, China.

Although the long-necked choristodere Hyphalosaurus is the most abundant tetrapod fossil in the renowned Yixian Formation fossil beds of Liaoning Province, China, the genus has only been briefly described from largely unprepared specimens. This paper provides a thorough osteological description of the type species Hyphalosaurus lingyuanensis and the con-generic species Hyphalosaurus baitaigouensis based on the study of fossils from several research institutions in China. The diagnoses for these two species are revised based on comparison of a large sample of specimens from the type area and horizon of each of the two species. The skull, better known in H. baitaigouensis, exhibits key choristodere synapomorphies including an elongate contact between the prefrontals and posteriorly expanded supratemporal fenestrae that strongly support the placement of the highly derived hyphalosaurids within Choristodera. Both species of Hyphalosaurus share a proportionally small head, an elongate neck, a relatively unspecialized appendicular skeleton and a long, dorsoventrally heightened tail. Soft tissue preservation in several specimens provides rare insight into the integument of an extinct group. The integument of Hyphalosaurus is made up of small polygonal scales with several parasagittal rows of large, keeled, ovoid scutes. These possibly ornamental scutes bear a strong resemblance to the rows of large scutes in the monjurosuchid choristodere Monjurosuchus splendens. Observations from a variety of growth stages reveal that significant ontogenetic change in the proportions of the body and limb bones occurred in both species of Hyphalosaurus.

Fish fingers: digit homologues in sarcopterygian fish fins

A defining feature of tetrapod evolutionary origins is the transition from fish fins to tetrapod limbs. A major change during this transition is the appearance of the autopod (hands, feet), which comprises two distinct regions, the wrist/ankle and the digits. When the autopod first appeared in Late Devonian fossil tetrapods, it was incomplete: digits evolved before the full complement of wrist/ankle bones. Early tetrapod wrists/ankles, including those with a full complement of bones, also show a sharp pattern discontinuity between proximal elements and distal elements. This suggests the presence of a discontinuity in the proximal-distal sequence of development. Such a discontinuity occurs in living urodeles, where digits form before completion of the wrist/ankle, implying developmental independence of the digits from wrist/ankle elements. We have observed comparable independent development of pectoral fin radials in the lungfish Neoceratodus (Osteichthyes: Sarcopterygii), relative to homologues of the tetrapod limb and proximal wrist elements in the main fin axis. Moreover, in the Neoceratodus fin, expression of Hoxd13 closely matches late expression patterns observed in the tetrapod autopod. This evidence suggests that Neoceratodus fin radials and tetrapod digits may be patterned by shared mechanisms distinct from those patterning the proximal fin/limb elements, and in that sense are homologous. The presence of independently developing radials in the distal part of the pectoral (and pelvic) fin may be a general feature of the Sarcopterygii.

The opisthotonic posture of vertebrate skeletons: postmortem contraction or death throes?

An extreme, dorsally hyperextended posture of the spine (opisthotonus), characterized by the skull and neck recurved over the back, and with strong extension of the tail, is observed in many well-preserved, articulated amniote skeletons (birds and other dinosaurs, pterosaurs, and at least placental mammals). Postmortem water transport may explain some cases of spinal curvature in fossil tetrapods, but we show how these can be distinguished from causes of the opisthotonic posture, which is a biotic syndrome. Traditional biotic explanations nearly all involve postmortem causes, and have included rigor mortis, desiccation, and contraction of tendons and ligaments. However, examination of the process of rigor mortis and experimental observations of drying and salinity in carcasses of extant animals show that these explanations of the “dead bird” (opisthotonic) posture account for few or no cases. Differential contraction of cervical ligaments after death also does not produce the opisthotonic posture. It is not postmortem contraction but perimortem muscle spasms resulting from various afflictions of the central nervous system that cause these extreme postures. That is, the opisthotonic posture is the result of “death throes,” not postmortem processes, and individuals so afflicted assumed the posture before death, not afterward. The clinical literature has long recognized that such afflicted individuals perish from asphyxiation, lack of nourishment or essential nutrients, environmental toxins, or viral infections, among other causes. Accepting the actual causes of the opisthotonic posture as perimortem and not postmortem provides insights into the causes of death of fossilized specimens, and also revises interpretations of paleoenvironmental conditions of many fossil deposits. The opisthotonic posture tells us more about the circumstances surrounding death than about what happened after death. Finally, the opisthotonic posture appears to have a phylogenetic signal: it is so far reported entirely in ornithodiran archosaurs (dinosaurs and pterosaurs) and in crown-group placentals, though the distribution in mammals may expand with further study. It seems important that the opisthotonic posture has been observed extensively only in clades of animals that are known or thought to have high basal metabolic rates: hypoxia and related diseases would be most likely to affect animals with high oxygen use rates.

Tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau, USA

Nonmarine fluvial, eolian and lacustrine strata of the Chinle and Glen Canyon groups on the southern Colorado Plateau preserve tetrapod body fossils and footprints that are one of the world's most extensive tetrapod fossil records across the Triassic–Jurassic boundary. We organize these tetrapod fossils into five, time-successive biostratigraphic assemblages (in ascending order, Owl Rock, Rock Point, Dinosaur Canyon, Whitmore Point and Kayenta) that we assign to the (ascending order) Revueltian, Apachean, Wassonian and Dawan land-vertebrate faunachrons (LVF). In doing so, we redefine the Wassonian and the Dawan LVFs. The Apachean–Wassonian boundary approximates the Triassic–Jurassic boundary. This tetrapod biostratigraphy and biochronology of the Triassic–Jurassic transition on the southern Colorado Plateau confirms that crurotarsan extinction closely corresponds to the end of the Triassic, and that a dramatic increase in dinosaur diversity, abundance and body size preceded the end of the Triassic.

The South African stereospondyl Lydekkerina huxleyi (Tetrapoda, Temnospondyli) from the Lower Triassic of Australia

The first tetrapod fossil from the Rewan Formation of the Galilee Basin, central Queensland, Australia, is identified as Lydekkerina huxleyi, a stereospondyl found elsewhere only in the Lystrosaurus Assemblage Zone of South Africa. Apomorphies shared with L. huxleyi are: anterior palatal vacuity with anterodorsal projections from its posterior margin; ventral surface of skull roof with series of thickened ridges (condition unknown in other lydekkerinids); and vomerine shagreen present (possible autapomorphic reversal). Restudy of the only other Australian lydekkerinid, Chomatobatrachus halei, shows it to be distinct from L. huxleyi. The Rewan Formation, undifferentiated in the Galilee Basin, can be correlated with the Rewan Group of the Bowen Basin, and to the early part of the Lystrosaurus Assemblage Zone of the Karoo Basin, South Africa, which are of Griesbachian age. Varying palaeoenvironments may contribute to the contrasting nature of the Australian and South African faunas.

NEW INFORMATION REGARDING THE HOLOTYPE OF SPINOSAURUS AEGYPTIACUS STROMER, 1915

In the autumn of 1912, the fossil collector Richard Markgraf, with financial support and direction from Bavarian paleontologist Ernst Freiherr Stromer von Reichenbach and the Bavarian Academy of Sciences, discovered the partial skeleton of a bizarre predatory dinosaur in Upper Cretaceous (early Cenomanian, ∼97 Ma, see Ismail et al., 1989; Barakat et al., 1993; El Beialy, 1994, 1995; Nabil and Hussein, 1994; Ismail and Soliman, 2001; Ibrahim, 2002; Gradstein et al., 2005) rocks of the Bahariya Formation exposed in the Bahariya Oasis of western Egypt (Fig. 1, see also Sereno et al., 1998; Nothdurft et al., 2002). This gigantic theropod, Spinosaurus aegyptiacus Stromer, 1915, possessed highly derived cranial and vertebral features sufficiently distinct for it to be designated as the nominal genus of the clade Spinosauridae (Stromer, 1915, 1936). Spinosaurids, currently definitively known only from Europe, South America, and Africa, are important because of the scarcity of Cretaceous Gondwanan tetrapod fossils (see Krause et al., 1999, 2003; Carrano et al., 2002; Lamanna et al., 2002). Moreover, fossils of Spinosaurus Stromer, 1915 and other spinosaurids are significant because of controversy surrounding the postulated paleoecology of these taxa (see discussions in Charig and Milner, 1997; Sereno et al., 1998; Sues et al., 2002). Questions related to spinosaurid paleoecology are particularly important in the Bahariya Formation, where Spinosaurus appears to have shared its habitat (see Stromer, 1936; Smith et al., 2001) with at least two other theropods in the size range of Tyrannosaurus Osborn, 1905 ( Bahariasaurus Stromer, 1934 and Carcharodontosaurus Stromer, 1931). Unfortunately, the holotype and only known indisputable specimen of S. aegyptiacus (BSP 1912 VIII 19) was lost during the night of 24/25 April 1944 in a British bombing raid of Munich (Nothdurft et al., …

Global Permian tetrapod biostratigraphy and biochronology

Abstract The most extensive Permian tetrapod (amphibian and reptile) fossil records from the western United States (New Mexico-Texas) and South Africa provide the basis for definition of 10 land-vertebrate faunachrons that encompass Permian time. These are (in ascending order): the Coyotean, Seymouran, Mitchellcreekian, Redtankian, Littlecrotonian, Kapteinskraalian, Gamkan, Hoedemakeran, Steilkransian and Platbergian. These faunachrons provide a biochronological framework with which to determine and discuss the age relationships of Permian tetrapod faunas. Their correlation to the marine time scale and its numerical calibrations indicate that the Coyotean is a relatively long time interval of about 20 Ma, whereas most of the other faunachrons are much shorter, about 1–2 Ma long each. The Platbergian may also be relatively long, 14 Ma, although this is not certain. This suggests slow rates of terrestrial tetrapod faunal turnover during most of the Early Permian and late Middle to Late Permian, but more rapid rates of turnover during the latest Early and most of the Middle Permian, especially during the explosive initial diversification of therapsids.