Batrachotomus

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Batrachotomus
Temporal range: Ladinian, Middle Triassic, 242–237  Ma
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Batrachotomus kupferzellensis.JPG
Reconstructed skeleton, Staatliches Museum für Naturkunde Stuttgart
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Loricata
Genus:† Batrachotomus
Gower, 1999
Species:
†B. kupferzellensis
Binomial name
†Batrachotomus kupferzellensis
Gower, 1999

Batrachotomus /ˌbætrəˈkɒtoʊməs/ is a genus of prehistoric archosaur. Fossils of this animal have been found in southern Germany and dated from the Ladinian stage of the Middle Triassic period, around 242 to 237 million years ago. Batrachotomus was described by palaeontologist David J. Gower 22 years after its discovery.

The locality where Batrachotomus lived was a swampy region and the name comes from the Greek batrachos/βάτραχος (frog) and tome/τομή (cutting, slicing), which refers to its preying on the large amphibian Mastodonsaurus . [1] In contrast with sprawling reptiles, like crocodiles, this large carnivore was very agile with locomotor superiority due to its erect stance. A remarkable feature seen on its back was a row of paired, flattened bony plates. Batrachotomus was possibly an early relative of Postosuchus , [2] which lived during the dawn of the dinosaurs.

Description

Artist's life restoration Batrachotomus1DB.jpg
Artist's life restoration
Size comparison of Batrachotomus Batrachotomus scale diagram.png
Size comparison of Batrachotomus

Batrachotomus was a heavily built, large quadrupedal reptile reaching 6 metres (20 ft) in length. A trait that characterized Batrachotomus, compared to other crurotarsans, was a series of paired small plates on its back which were attached to each vertebra. [3] These bony deposits forming scales are called osteoderms. [3] Flattened and leaf-shaped, these extended from behind the head along the column and reducing in size, ended at the tail. [3] There is also evidence that osteoderms were present on the ventral region of the tail, as seen in Ticinosuchus ferox , and even on the flank, belly and limbs. [3] [4]

Like rauisuchians, Batrachotomus walked with an erect posture, although the limbs were not located directly under the trunk. The limbs were not equal in length as the forelimbs were about 70% of the hindlimbs. [3] [5] The toe bones (phalanges) are poorly preserved and the only well known bone is a fifth metatarsal (bone in hindlimbs attached to the toe bones) which was hooked in shape. [3] However, hypotheses suggest that probably each forelimb had four toes and each hindlimb five. [6]

Skull, Staatliches Museum fur Naturkunde Stuttgart Batrachotomus kupferzellensis 2.JPG
Skull, Staatliches Museum für Naturkunde Stuttgart

Batrachotomus had a tall and narrow skull estimated at 40 to 50 cm (1.3 to 1.6 ft) in length. [7] It had five pairs of fenestrae (skull openings), two pairs of which were for the eyes (called orbits) and the nostrils. Behind the orbits were two temporal fenestrae. These holes probably helped to reduce the weight of the skull and enabled the jaw to open more widely. [8] As a typical archosaur, Batrachotomus had two antorbital fenestrae between the orbits and nostrils, and a fifth pair of small openings at the rear part of the lower jaw.

The jaws contained sharp teeth which were compressed laterally and unequal in size and shape, [7] [9] and this variation of tooth shape is known as heterodonty. [7] [10] The teeth on the premaxillae (bones at the very tip of the upper jaw) were slender, unlike those of the maxillae (the main tooth-bearing bones in the upper jaw) which had a straight posterior edge. [11] The upper jaw bore 30 teeth, with each premaxilla carrying about 4 teeth and each maxilla 11, while the lower jaw held 22 teeth. [9]

Discovery and history

The Kupferzell locality in Germany, where fossils of Batrachotomus have been discovered. Batrachotomus Germany localisation map.jpg
The Kupferzell locality in Germany, where fossils of Batrachotomus have been discovered.

Remains of Batrachotomus have been found in southern Germany, mainly in the Kupferzell fossil locality in northern Baden-Württemberg. Fossil collector Johann G. Wegele discovered the first specimens in a 1977 excavation at the Erfurt Formation, dated from the Longobardian (late Ladinian) age. [12] [13] Other remains attributed to Batrachotomus have been collected in Vellberg-Eschenau, about 10 km east of Schwäbisch Hall, and in Crailsheim. The most notable are from Vellberg-Eschenau, which are represented by well preserved ribs and vertebrae (MHI 1895), and evidence of forelimbs and hindlimbs (SMNS 90018). [13] Batrachotomus today is displayed in the Muschelkalk Museum, Ingelfingen, Stuttgart.

The fossils recovered from a marlstone remained undescribed until 1999 and palaeontologists referred to the genus simply as "rauisuchid" or "Kupferzellia". [7] [12] In 1999, palaeontologist David J. Gower described the holotype (SMNS 52970) from the 1977 excavation, which is the largest specimen of the genus, [12] [13] comprised by incomplete skull and postcranial material. [1] Anatomy of the braincase (SMNS 80260) was made three years later, shedding light on the evolutionary relationships of the poorly known group of Rauisuchia. [14] In 2009, Gower and Rainer R. Schoch reported a detailed reconstruction of the postcranial skeleton for the first time. [15]

Classification

Skeletal elements, Museum am Lowentor, Stuttgart Batrachotomus kupferzellensis fossils.jpg
Skeletal elements, Museum am Lowentor, Stuttgart

Batrachotomus was a prestosuchid, a member of a family of carnivorous archosaurs within the larger group Rauisuchia. The family name "Prestosuchidae" was established in 1966 by American paleontologist Alfred Romer. Prestosuchids were quadrupedal reptiles, medium to large in size, characterized by erect posture, large and narrow skull and large antorbital openings. [16]

Attention was first brought to Batrachotomus in 1993 by Michael Parrish, a palaeontologist at Northern Illinois University. Parrish hypothesized that Batrachotomus (then "Kupferzellia") belonged to the family of Rauisuchidae, another clade of carnivorous reptiles, and species of Rauisuchus . [7] [17] However, the description of the braincase and a revisited cladistic analysis by Benton and Walker, showing the close relationships between Batrachotomus and Prestosuchus, led to the transfer of Batrachotomus to the family Prestosuchidae. [14] [18]

Sterling J. Nesbitt (2011) revised the classification of basal archosaurs, and using the most comprehensive phylogenetic analysis for this group (to date) found Prestosuchidae to be non-monophyletic. The members of this clade were recovered as basal loricatan, of which Batrachotomus was found to be the most derived i.e. most closely related to the clade containing Crocodylomorpha and Rauisuchidae. [19] Subsequent derivatives of this analysis further support this hypothesis. [20] [21] In a yet to be formally published revision of Heptasuchus , a medium/large-sized (~6.5 m long) "rauisuchian" from the upper Chugwater Group of Wyoming, it was recovered as the sister taxon of Batrachotomus using a derivative of Nesbitt (2011) analysis. [22]

The cladogram below follows an analysis by Sterling J. Nesbitt (2011): [23]

Model (background) in Triassic environment Triassic landscape 43.jpg
Model (background) in Triassic environment
Archosauria  

Paleoecology

Since 1977, the rich vertebrate fauna found at Baden-Württemberg reflects a moist region of the Middle Triassic in Germany. Along with Batrachotomus, palaeontologists recovered remains of fishes, amphibians, such as Gerrothorax and Mastodonsaurus, and even animals like nothosaurs and the distinct marine reptile Tanystropheus . [12] The flora of the locality consisted of horsetails, ferns, cycads and conifers, suggesting that there was rich vegetation. [24]

Related Research Articles

<span class="mw-page-title-main">Rauisuchia</span> Informal group of Triassic archosaurs with pillar-erect posture

"Rauisuchia" is a paraphyletic group of mostly large and carnivorous Triassic archosaurs. Rauisuchians are a category of archosaurs within a larger group called Pseudosuchia, which encompasses all archosaurs more closely related to crocodilians than to birds and other dinosaurs. First named in the 1940s, Rauisuchia was a name exclusive to Triassic archosaurs which were generally large, carnivorous, and quadrupedal with a pillar-erect hip posture, though exceptions exist for all of these traits. Rauisuchians, as a traditional taxonomic group, were considered distinct from other Triassic archosaur groups such as early dinosaurs, phytosaurs, aetosaurs, and crocodylomorphs.

<i>Postosuchus</i> Genus of reptiles

Postosuchus, meaning "Crocodile from Post", is an extinct genus of rauisuchid reptiles comprising two species, P. kirkpatricki and P. alisonae, that lived in what is now North America during the Late Triassic. Postosuchus is a member of the clade Pseudosuchia, the lineage of archosaurs that includes modern crocodilians. Its name refers to Post Quarry, a place in Texas where many fossils of the type species, P. kirkpatricki, were found. It was one of the apex predators of its area during the Triassic, larger than the small dinosaur predators of its time. It was a hunter which probably preyed on large bulky herbivores like dicynodonts and many other creatures smaller than itself.

<i>Euparkeria</i> Extinct genus of reptiles

Euparkeria is an extinct genus of archosauriform reptile from the Triassic of South Africa. Euparkeria is close to the ancestry of Archosauria, the reptile group that includes crocodilians, pterosaurs, and dinosaurs.

<span class="mw-page-title-main">Trilophosauridae</span> Extinct family of reptiles

Trilophosaurs are lizard-like Triassic allokotosaur reptiles related to the archosaurs. The best known genus is Trilophosaurus, a herbivore up to 2.5 metres long. It had a short, unusually heavily built skull, equipped with massive, broad flattened cheek teeth with sharp shearing surfaces for cutting up tough plant material. Teeth are absent from the premaxilla and front of the lower jaw, which in life were probably equipped with a horny beak.

<span class="mw-page-title-main">Poposauridae</span> Extinct family of reptiles

Poposauridae is a family of large carnivorous archosaurs which lived alongside dinosaurs during the Late Triassic. They were around 2.5 to 5 metres long. Poposaurids are known from fossil remains from North and South America. While originally believed to be theropod dinosaurs, cladistic analysis has shown them to be more closely related to crocodiles.

<i>Gracilisuchus</i> Genus of fossil reptiles

Gracilisuchus is an extinct genus of tiny pseudosuchian from the Late Triassic of Argentina. It contains a single species, G. stipanicicorum, which is placed in the clade Suchia, close to the ancestry of crocodylomorphs. Both the genus and the species were first described by Alfred Romer in 1972.

<span class="mw-page-title-main">Rauisuchidae</span> Extinct family of reptiles

Rauisuchidae is a group of large predatory Triassic archosaurs. Some disagreement exists over which genera should be included in the Rauisuchidae and which should be in the related Prestosuchidae and Poposauridae, and indeed whether these should even be thought of as separate valid families. Rauisuchids occurred throughout much of the Triassic, and may have first occurred in the Early Triassic if some archosaurian taxa such as Scythosuchus and Tsylmosuchus are considered to be within the family.

<span class="mw-page-title-main">Prestosuchidae</span> Extinct family of reptiles

Prestosuchidae is a polyphyletic grouping of carnivorous archosaurs that lived during the Triassic. They were large active terrestrial apex predators, ranging from around 2.5 to 7 metres in length. They succeeded the Erythrosuchidae as the largest archosaurs of their time. While resembling erythrosuchids in size and some features of the skull and skeleton, they were more advanced in their erect posture and crocodile-like ankle, indicating more efficient gait. "Prestosuchids" flourished throughout the whole of the middle, and the early part of the late Triassic, and fossils are so far known from Europe, India, Africa (Tanzania), Argentina, and Paleorrota in Brazil. However, for a long time experts disagree regarding the phylogenetic relationships of the group, what genera should be included, and whether indeed the "Prestosuchidae" constitute a distinct family.

<i>Erythrosuchus</i> Extinct genus of reptiles

Erythrosuchus is an extinct genus of archosauriform reptiles from the Triassic of South Africa. Remains have been found from the Cynognathus Assemblage Zone of the Beaufort Group in the Karoo of South Africa.

<i>Luperosuchus</i> Extinct genus of reptiles

Luperosuchus is an extinct genus of loricatan pseudosuchian reptile which contains only a single species, Luperosuchus fractus. It is known from the Chañares Formation of Argentina, within strata belonging to the latest Ladinian stage of the late Middle Triassic, or the earliest Carnian of the Late Triassic. Luperosuchus was one of the largest carnivores of the Chañares Formation, although its remains are fragmentary and primarily represented by a skull with similarities to Prestosuchus and Saurosuchus.

Yarasuchus is an extinct genus of avemetatarsalian archosaur that lived during the Anisian stage of the Middle Triassic of India. The genus was named and described in 2005 from a collection of disarticulated but fairly complete fossil material found from the Middle Triassic Yerrapalli Formation. The material is thought to be from two individuals, possibly three, with one being much more complete and articulated than the other. The type and only species is Y. deccanensis. Yarasuchus was a quadruped roughly 2–2.5 metres (6.6–8.2 ft) long, with an elongated neck and tall spines on its vertebrae. Unlike other quadrupedal Triassic reptiles, the limbs and shoulders of Yarasuchus were slender, and more like those of ornithodirans.

Arganasuchus is an extinct genus of "rauisuchian" (loricatan) archosaur. It is known from a single species, Arganasuchus dutuiti. Fossils of this genus have been found in Upper Triassic rocks of the Argana Basin, Morocco. Though its remains were initially referred to Ticinosuchus when discovered during the 1970s, in 2007 it was identified as a distinct genus with unique features of the pubis and maxilla. Arganasuchus also had several anatomical details in common with Batrachotomus, Fasolasuchus, and Postosuchus, though its relations with other loricatans remains unresolved. Arganasuchus is considered a carnivore due to its large, knife-shaped teeth.

<i>Heptasuchus</i> Extinct genus of reptiles

Heptasuchus is an extinct genus of loricatan pseudosuchian known from the Middle or Late Triassic upper Chugwater Group of Wyoming, United States. It contains a single species, Heptasuchus clarki, the first formally recognized "rauisuchian" or loricatan pseudosuchian from North America.

Procerosuchus is an extinct genus of loricatan archosaur. Fossils have been collected from the Late Triassic Santa Maria Formation in Geopark of Paleorrota, Rio Grande do Sul, Brazil, which is Carnian in age. The genus was first described by the German paleontologist Friedrich von Huene in 1942.

Stagonosuchus is an extinct genus of loricatan, or possibly a species of Prestosuchus. Fossils have been found from the Late Triassic Manda Formation in Tanzania that are Anisian in age.

<i>Youngosuchus</i> Extinct genus of reptiles

Youngosuchus is an extinct genus of archosaur from the Middle Triassic of China. The type species is Y. sinensis. Y. sinensis was first described in 1973 as a new species of the erythrosuchid Vjushkovia. In 1985, it was reassigned as its own genus of rauisuchid. A 1992 study supported the original classification of Youngosuchus sinensis as an erythrosuchid, but more recent studies classify it as a "rauisuchian"-grade loricatan archosaur completely unrelated to Vjushkovia, which is most likely a synonym of Garjainia.

<span class="mw-page-title-main">Paracrocodylomorpha</span> Clade of reptiles

Paracrocodylomorpha is a clade of pseudosuchian archosaurs. The clade includes the diverse and unusual group Poposauroidea as well as the generally carnivorous and quadrupedal members of Loricata, including modern crocodylians. Paracrocodylomorpha was named by paleontologist J. Michael Parrish in 1993, although the group is now considered to encompass more reptiles than his original definition intended. The most recent definition of Paracrocodylomorpha, as defined by Sterling Nesbitt in 2011, is "the least inclusive clade containing Poposaurus and Crocodylus niloticus. Most groups of paracrocodylomorphs became extinct at the end of the Triassic period, with the exception of the crocodylomorphs, from which crocodylians such as crocodiles and alligators evolved in the latter part of the Mesozoic.

<span class="mw-page-title-main">Erfurt Formation</span>

The Erfurt Formation, also known as the Lower Keuper, is a stratigraphic formation of the Keuper group and the Germanic Trias supergroup. It was deposited during the Ladinian stage of the Triassic period. It lies above the Upper Muschelkalk and below the Middle Keuper.

<span class="mw-page-title-main">Azendohsauridae</span> Extinct family of reptiles

Azendohsauridae is a family of allokotosaurian archosauromorphs that lived during the Middle to Late Triassic period, around 242-216 million years ago. The family was originally named solely for the eponymous Azendohsaurus, marking out its distinctiveness from other allokotosaurs, but as of 2022 the family now includes four other genera: the basal genus Pamelaria, the large horned herbivore Shringasaurus, and two carnivorous genera grouped into the subfamily-level subclade Malerisaurinae, Malerisaurus and Puercosuchus, and potentially also the dubious genus Otischalkia. Most fossils of azendohsaurids have a Gondwanan distribution, with multiple species known across Morocco and Madagascar in Africa as well as India, although fossils of malerisaurine azendohsaurids have also been found in the southwestern United States of North America.

<i>Polymorphodon</i> Extinct genus of reptiles

Polymorphodon is an extinct genus of archosauriform reptile from the Middle Triassic of Germany. The only known species is Polymorphodon adorfi, discovered in Lower Keuper deposits at a quarry in Eschenau, Germany. Polymorphodon is notable for its heterodont dentition, with long and conical premaxillary teeth followed by thin maxillary teeth with large serrations. Maxillary teeth near the back of the mouth are short and leaf-shaped, similar to some living and extinct reptiles with a herbivorous or omnivorous diet. This may suggest that Polymorphodon had some reliance on plants in its diet, a rarity among basal archosauriforms, most of which are carnivores.

References

Notes
  1. 1 2 Gower (1999), p. 6.
  2. ↑ Gower (1999), p. 1.
  3. 1 2 3 4 5 6 Gower and Schoch (2009), p. 117.
  4. ↑ Gower and Schoch (2009), p. 104.
  5. ↑ Gower and Schoch (2009), p. 109.
  6. ↑ Gower and Schoch (2009), p. 119 (Figure 8).
  7. 1 2 3 4 5 Gower (1999), p. 7.
  8. ↑ Benton (2005), p. 112.
  9. 1 2 Gower (1999), p. 37.
  10. ↑ Gower (1999), p. 38.
  11. ↑ Gower (1999), pp. 37–38.
  12. 1 2 3 4 Gower (1999), p. 5.
  13. 1 2 3 Gower and Schoch (2009), p. 121.
  14. 1 2 Gower (2002), p. 49.
  15. ↑ Gower and Schoch (2009), p. 103.
  16. ↑ Sill (1974), p. 317.
  17. ↑ Parrish (1993), p. 301.
  18. ↑ Benton and Walker (2002), pp. 40–41.
  19. ↑ Nesbitt, S. J. (2011). "The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi:10.1206/352.1. hdl: 2246/6112 . S2CID   83493714.
  20. ↑ Li, C.; Wu, X. C.; Zhao, L. J.; Sato, T.; Wang, L. T. (2012). "A new archosaur (Diapsida, Archosauriformes) from the marine Triassic of China". Journal of Vertebrate Paleontology. 32 (5): 1064. doi:10.1080/02724634.2012.694383. S2CID   86797826.
  21. ↑ Sues, H. D.; Schoch, R. R. (2013). "Reassessment of cf. Halticosaurus orbitoangulatus from the Upper Triassic (Norian) of Germany - a pseudosuchian, not a dinosaur". Zoological Journal of the Linnean Society. 168 (4): 859. doi: 10.1111/zoj.12038 .
  22. ↑ Zawiskie, J.M.; Dawley, R.M.; Nesbitt, S.J. (2011). "The relationships and type locality of Heptasuchus clarki, Chugwater Group (Middle to Upper Triassic), Southeastern Big Horn Mountains, Wyoming, USA". Journal of Vertebrate Paleontology. 31 (Supp. 1): 219. doi:10.1080/02724634.2011.10635174. S2CID   210915628.
  23. ↑ Sterling J. Nesbitt (2011). "The Early Evolution of Archosaurs: Relationships and the Origin of Major Clades". Bulletin of the American Museum of Natural History. 352: 1–292. doi: 10.1206/352.1 . hdl:2246/6112. S2CID   83493714.
  24. ↑ Rozynek (2008), p. 4.
Sources

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