Erpetosuchidae

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Erpetosuchidae
Temporal range: Middle - Late Triassic, 247–208.5  Ma
Parringtonia gracilis.jpg
Skeletal mount of Parringtonia at the FMNH
Scientific classification OOjs UI icon edit-ltr.svg
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Clade: Archosauria
Clade: Pseudosuchia
Clade: Suchia
Family: Erpetosuchidae
Watson, 1917
Subgroups

Erpetosuchidae is an extinct family of pseudosuchian archosaurs. Erpetosuchidae was named by D. M. S. Watson in 1917 to include Erpetosuchus. [1] It includes the type species Erpetosuchus granti from the Late Triassic of Scotland, Erpetosuchus sp. from the Late Triassic of eastern United States and Parringtonia gracilis from the middle Middle Triassic of Tanzania; [2] the group might also include Dyoplax arenaceus from the Late Triassic of Germany, [3] Archeopelta arborensis and Pagosvenator candelariensis from Brazil and Tarjadia ruthae from Argentina. [4]

Contents

Description

General features

Erpetosuchids were lithe but well-armored carnivorous pseudosuchians. Two rows of overlapping armored plates (osteoderms) extended from the neck to the tail, supplemented by an additional row on the back and tail and small oval-shaped osteoderms on the legs and possibly the arms as well. The osteoderms were unusually sculptured by deep pits and ranged in shape and thickness between taxa. [4]

Erpetosuchids also characteristically had upper teeth restricted to the front part of the mouth. While Erpetosuchus and Parringtonia had unserrated and only slightly mediolaterally compressed teeth, Tarjadia had thin and serrated teeth more similar to other carnivorous archosauriforms. Erpetosuchids also had broad maxillae with antorbital fenestrae set approximately in the middle of the deep antorbital fossa, which in turn was completely surrounded by bony ridges. Under the ridge which composes the ventral edge of the antorbital fossa, the maxilla (particularly the rear part) slopes inwards towards the teeth. Although erpetosuchid skulls were not low and flat like those of some archosauriform groups, they were broader than those of other basal pseudosuchians, particularly behind the orbits, which were large and pointed upwards. [2] [4]

They also had a deep groove or pit on the top surface of their wide neural spines, a condition quite different from that of other archosaurs. The neural spines were taller on the tail than on the back. [4]

Erpetosuchus and Parringtonia

Life restoration of Erpetosuchus Erpetosuchus BW.jpg
Life restoration of Erpetosuchus

When Erpetosuchidae was first defined to include Erpetosuchus and Parringtonia, three synapomorphies or shared characteristics were identified for the family: teeth restricted to the anterior half of the maxilla, a posterior half of the maxilla that is thicker than it is tall, and no tooth serrations (although Tarjadia was known to have serrated teeth). Other possible synapomorphies of the two taxa were considered tentative due to having not yet been sampled in the cladistic analysis. In Erpetosuchus, the medially inclined lower external surface of the maxilla continues posteriorly onto the jugal, exposing much of the external surface of the jugal in ventral view. This morphology unites the North American and European specimens of Erpetosuchus with Parringtonia gracilis. Other potential synapomorphies include a hypertrophied tuber hypothesized for the attachment of the m. triceps brachii on the posterolateral surface of the proximal scapula blade. Unlike other archosauriforms that have a small tuber in the same location, the size of the tuber in erpetosuchids is exceptionally large in relation to the overall size of the scapula. Furthermore, as Krebs (1976) hypothesized the scapula blade slightly arc anteriorly in both taxa. However, this condition is similar to that of other archosaurs, like Postosuchus kirkpatricki . [2]

While Erpetosuchus granti and Erpetosuchus sp. are nearly indistinguishable, the scapula of Parringtonia differs from E. granti in that it has a small bump or tubercle over its shoulder socket, osteoderms that are nearly square instead of being anteroposteriorly longer than wide, and a foramen (or hole) on the outer surface of the maxilla. Parringtonia has five tooth sockets, Erpetosuchus gracilis only four, and Erpetosuchus sp. six or more (up to nine). Furthermore, Erpetosuchus sp. has a proportionally taller ascending process of the maxilla than Parringtonia. [2]

Other members

Dyoplax, a controversial pseudosuchian from Germany, has been proposed to be a close relative of Erpetosuchus. Some similarities between the two taxa include the structure of their osteoderms (including unusual small cervical osteoderms), a recessed antorbital fenestra, ridges completely surrounding the antorbital fossa, large and upward-pointing orbits, and slender limbs. However, the preservation of the only known specimen of Dyoplax, a sandstone mold, makes analysis difficult, and Dyoplax lacks many of the features that characterize other erpetosuchids. Nevertheless, the relation of Dyoplax shares more similarities with Erpetosuchidae than with other groups it has been proposed to be related to, such as Aetosauria and "Sphenosuchia". [3]

New specimens of Tarjadia have doubted its previous classification as a doswellid and instead supports it as a member of Erpetosuchidae. Support for this new assignment is seemingly robust, with Tarjadia possessing many erpetosuchid features. Some of these features include a lack of posterior maxillary teeth, the presence of neural spine pits, an erpetosuchid-style maxilla, and archosaurian traits which contrast with those of the doswellids, which are non-archosaurian archosauriforms. This new classification also places the former doswellid Archeopelta as an erpetosuchid, as it is a very close relative of Tarjadia. [4]

Pagosvenator is a Brazilian genus which has been allied with the ornithosuchids prior to receiving a formal description in 2018. Despite only being known from a skull and a few vertebrae and osteoderms, it shares similarities with several erpetosuchids. Although its description only compared it with Erpetosuchus and Parringtonia, its assignment to this family does have some support. It shares a few traits with these other genera, such as maxillary teeth at only the front of the mouth and a portion of the maxilla under the lacrimal which is higher than long. [5]

Classification

Erpetosuchidae is a stem-based taxon first defined by Nesbitt & Butler (2012) as "the most inclusive clade containing Erpetosuchus granti but not Passer domesticus , Postosuchus kirkpatricki , Crocodylus niloticus , Ornithosuchus longidens or Aetosaurus ferratus ". A phylogenetic analysis conducted by Nesbitt & Butler (2012) showed that Parringtonia gracilis and Erpetosuchus granti form a well-supported clade (Erpetosuchidae) within Archosauria. This analysis was based on a modified version of Nesbitt (2011) analysis, the most extensive early archosaur phylogeny to date. The results of this analysis were very similar to those of Nesbitt (2011). However, the addition of Parringtonia and Erpetosuchus decreased resolution at the base of Archosauria and resulted in a strict consensus tree with a large polytomy or unresolved evolutionary relationship. This polytomy contained Erpetosuchidae, Avemetatarsalia, Ornithosuchidae, Aetosauria and Revueltosaurus clade, Ticinosuchus and Paracrocodylomorpha clade, Gracilisuchus , and Turfanosuchus . Of the other trees produced in the analysis, Erpetosuchidae takes six possible phylogenetic positions within Archosauria. Five out of six are within the Pseudosuchia, meaning that Parringtonia and Erpetosuchus are probably crocodile-line archosaurs as was previously thought. However, none of the possible positions are within the Paracrocodylomorpha, meaning that Parringtonia and Erpetosuchus are not closely related to Crocodylomorpha. Below are the possible positions within Nesbitt's phylogeny, marked by dashed lines: [2]

Archosauromorpha

The exclusion of Gracilisuchus and Turfanosuchus results in a more resolved topology, placing Erpetosuchidae at the base of Suchia as the sister taxon of aetosaurs plus Revueltosaurus clade. This relationship is weakly supported by only the two character states: posterior portion of the maxilla ventral to the antorbital fenestra expands dorsoventrally and two paramedian pairs of osteoderms. When E. granti was solely used to represent Erpetosuchidae, Gracilisuchus and Turfanosuchus were recovered as basal suchians, in polytomy with Ticinosuchus plus Paracrocodylomorpha and E. granti plus (aetosaurs plus Revueltosaurus) clade. Below is a cladogram after the exclusion of Gracilisuchus and Turfanosuchus (Avemetatarsalia, Loricata and Poposauroidea have been collapsed). [2]

Archosauromorpha

In 2017, a phylogenetic analysis by Ezcurra et al. provided a novel reinterpretation of basal pseudosuchian classification. This analysis reported that Ornithosuchidae formed a clade with Erpetosuchidae, and that this clade formed the sister taxon of Aetosauria (and presumably Revueltosaurus as well) at the base of Suchia. This contrasts with previous assumptions about pseudosuchian taxonomy, such as the idea that ornithosuchids were outside Suchia or that phytosaurs were not pseudosuchians. Although phylogenetic support for the Aetosauria+Ornithosuchidae+Erpetosuchidae clade is low, the Ornithosuchidae+Erpetosuchidae clade (as well as Erpetosuchidae itself) were well-supported. This finding, along with other hypotheses supported by this analysis, have important implications for pseudosuchian classification. The following cladogram is a simplified version of the strict reduced consensus tree of that study, and excludes non-eucrocopodan archosauromorphs. [4]

Eucrocopoda

The close relationship between erpetosuchids, aetosaurs, and Revueltosaurus is also supported by braincase features according to complete braincase material assignable to Parringtonia. For example, they all have slanted supraoccipital bones, a part of the braincase above the foramen magnum (spinal cord hole). In addition, the upper edge of the foramen magnum possesses small platforms which may have articulated with neck bones such as the proatlas, a rudimentary vertebra in front of the atlas bone. [6]

The 2018 description of the new erpetosuchid Pagosvenator supports two phylogenetic positions for the family in particular. One of these positions is at the base of Pseudosuchia in a clade with ornithosuchids. The other position places them inside Suchia, as the sister family to the clade including gracilisuchids and Paracrocodylomorpha. Although these two positions seem to be equally likely, they are also far more likely than any other possible position. However, this source was written prior to the publication of Ezcurra et al. (2017), despite being published later, and therefore does not discuss the implications of that source. This also means that Tarjadia and Archeopelta were not yet considered erpetosuchids, and thus they were not featured in the phylogenetic analysis. [5]

Related Research Articles

Phytosaurs are an extinct group of large, mostly semiaquatic Late Triassic archosauriform reptiles. Phytosaurs belong to the order Phytosauria. and are sometimes referred to as parasuchians. Phytosauria, Parasuchia, Parasuchidae, and Phytosauridae have often been considered equivalent groupings containing the same species. Some recent studies have offered a more nuanced approach, defining Parasuchidae and Phytosauridae as nested clades within Phytosauria as a whole. Phytosaurs were long-snouted and heavily armoured, bearing a remarkable resemblance to modern crocodilians in size, appearance, and lifestyle, as an example of convergence or parallel evolution

<span class="mw-page-title-main">Aetosaur</span> Extinct order of heavily armoured reptiles

Aetosaurs are heavily armored reptiles belonging to the extinct order Aetosauria. They were medium- to large-sized omnivorous or herbivorous pseudosuchians, part of the branch of archosaurs more closely related to crocodilians than to birds and other dinosaurs. All known aetosaurs are restricted to the Late Triassic, and in some strata from this time they are among the most abundant fossil vertebrates. They have small heads, upturned snouts, erect limbs, and a body ornamented with four rows of plate-like osteoderms. Aetosaur fossil remains are known from Europe, North and South America, parts of Africa, and India. Since their armoured plates are often preserved and are abundant in certain localities, aetosaurs serve as important Late Triassic tetrapod index fossils. Many aetosaurs had wide geographic ranges, but their stratigraphic ranges were relatively short. Therefore, the presence of particular aetosaurs can accurately date a site in which they are found.

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

Revueltosaurus is an extinct genus of suchian pseudosuchian from Late Triassic deposits of New Mexico, Arizona and North Carolina, United States. Many specimens, mostly teeth, have been assigned to Revueltosaurus over the years. Currently, three species are included in this genus, all of which were originally thought to represent monospecific genera of basal ornithischian dinosaurs. Revueltosaurus was about 1 meter long.

<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">Pseudosuchia</span> Clade of reptiles

Pseudosuchia is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely related to crocodilians than to birds. Pseudosuchians are also informally known as "crocodilian-line archosaurs". Despite Pseudosuchia meaning "false crocodiles", the name is a misnomer as true crocodilians are now defined as a subset of the group.

<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>Erpetosuchus</i> Extinct genus of reptiles

Erpetosuchus is an extinct genus of pseudosuchian from the Late Triassic. The type species of Erpetosuchus is E. granti. It was first described by E. T. Newton in 1894 for remains found in northeastern Scotland, including four specimens from the latest Carnian Lossiemouth Sandstone Formation. Additional remains of Erpetosuchus have been found in the New Haven Formation of Connecticut in the eastern United States, although they were not attributed to the species E. granti. The relationship of Erpetosuchus to other archosaurs is uncertain. In 2000 and 2002, it was considered a close relative of the group Crocodylomorpha, which includes living crocodylians and many extinct relatives. However, this relationship was questioned in a 2012 analysis that found the phylogenetic placement of Erpetosuchus to be very uncertain.

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

Turfanosuchus is a genus of archosauriform reptile, likely a gracilisuchid archosaur, which lived during the Middle Triassic (Anisian) of northwestern China. The type species, T. dabanensis, was described by C.C. Young in 1973, based on a partially complete but disarticulated fossil skeleton found in the Kelamayi Formation of the Turfan Basin.

<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.

Euscolosuchus is an extinct genus of suchian archosaurs from the Late Triassic of Virginia. It is probably an aetosauriform, as the sister taxon to Acaenasuchus and a relative of aetosaurs.

<span class="mw-page-title-main">Aetosaurinae</span> Extinct subfamily of reptiles

Aetosaurinae is one of the two main clades of aetosaurs, the other being Desmatosuchia. It is a stem-based taxon defined as all aetosaurs more closely related to Aetosaurus than Desmatosuchus. Aetosaurinae currently comprises Aetosaurus, similar forms such as Coahomasuchus and Stenomyti, and the widespread and successful aetosaur clade Typothoracinae.

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

Parringtonia is an extinct genus of Triassic archosaur within the family Erpetosuchidae, known from the type species Parringtonia gracilis. It is known from a single specimen, NHMUK R8646, found from the Anisian-age Manda Formation of Tanzania. This specimen, like most archosaur material from the Manda Formation, is fragmentary, including only a maxilla and a few postcranial bones. They show similarities with those of another archosaur called Erpetosuchus, known from the Middle Triassic of Scotland and the eastern United States. The phylogenetic placement of Parringtonia and Erpetosuchus are uncertain; some studies placed them close to the group Crocodylomorpha, which includes all modern crocodylians and many extinct forms that diversified after the Triassic, but this relationship has more recently been questioned.

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

Yonghesuchus is an extinct genus of Late Triassic archosaur reptile. Remains have been found from the early Late Triassic Tongchuan Formation in Shanxi, China. It is named after Yonghe County, the county where fossils were found. Currently only one species, Y. sangbiensis, is known. The specific name refers to Sangbi Creek, as fossils were found in one of its banks.

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

Suchia is a clade of archosaurs containing the majority of pseudosuchians. It was defined as the least inclusive clade containing Aetosaurus ferratus, Rauisuchus tiradentes, Prestosuchus chiniquensis, and Crocodylus niloticus by Nesbitt (2011). Generally the only pseudosuchian group which is omitted from Suchia is the family Ornithosuchidae, although at least one analysis classifies ornithosuchids as close relatives of erpetosuchids and aetosaurs. Phytosaurs are also excluded from Suchia, although it is not certain whether they qualify as pseudosuchians in the first place.

<span class="mw-page-title-main">Poposauroidea</span> Extinct clade of reptiles

Poposauroidea is a clade of advanced pseudosuchians. It includes poposaurids, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as Qianosuchus and Lotosaurus. It excludes most large predatory quadrupedal "rauisuchians" such as rauisuchids and "prestosuchids". Those reptiles are now allied with crocodylomorphs in a clade known as Loricata, which is the sister taxon to the poposauroids in the clade Paracrocodylomorpha. Although it was first formally defined in 2007, the name "Poposauroidea" has been used for many years. The group has been referred to as Poposauridae by some authors, although this name is often used more narrowly to refer to the family that includes Poposaurus and its close relatives.

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

Bathyotica is a clade of crurotarsan archosaurs that includes the superorder Crocodylomorpha and its sister taxon Erpetosuchus, a small Triassic suchian. Bathyotica was named in a 2002 phylogenetic study of Erpetosuchus. The genus was found to be closely related to crocodylomorphs, and Bathyotica was erected to encompass both taxa.

<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.

Pagosvenator is an extinct genus of erpetosuchid from the Mid-Late Triassic Dinodontosaurus Assemblage Zone of the Santa Maria Supergroup of Brazil. The type species, Pagosvenator candelariensis, was described in 2018.

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

Dynamosuchus is an extinct genus of pseudosuchian archosaurs from the family Ornithosuchidae. It is known from a single species, Dynamosuchus collisensis, which is based on a partial skeleton from the Santa Maria Formation of Brazil. Dynamosuchus is considered a close relative of Venaticosuchus, which is known from the Ischigualasto Formation of Argentina. Ornithosuchids are one of many groups which lived in the Santa Maria and Ischigualasto Formations, which formed at approximately the same time and were ecologically similar. As a large scavenging reptile, Dynamosuchus helps to illuminate the trophic structure of the Santa Maria Formation. It also supports the hypothesis that ornithosuchids had diversified throughout South America by the start of the Carnian, and were not originally endemic to the Ischigualasto-Villa Unión Basin.

<span class="mw-page-title-main">Aetosauriformes</span> Extinct clade of reptiles

Aetosauriformes is an extinct clade of early-diverging pseudosuchians. It includes the aetosaurs, a group of heavily armoured and at least partially herbivorous pseudosuchians, as well as the closely related genera Acaenasuchus, Euscolosuchus and Revueltosaurus.

References

  1. Benton, M. J.; Walker, A. D. (2002). "Erpetosuchus, a crocodile-like basal archosaur from the Late Triassic of Elgin, Scotland". Zoological Journal of the Linnean Society. 136: 25–47. doi: 10.1046/j.1096-3642.2002.00024.x .
  2. 1 2 3 4 5 6 Nesbitt, S. J.; Butler, R. J. (2012). "Redescription of the archosaur Parringtonia gracilis from the Middle Triassic Manda beds of Tanzania, and the antiquity of Erpetosuchidae". Geological Magazine. 150 (2): 225–238. doi:10.1017/S0016756812000362. S2CID   232175772.
  3. 1 2 Michael W. Maisch; Andreas T. Matzke; Thomas Rathgeber (2013). "Re-evaluation of the enigmatic archosaur Dyoplax arenaceus O. Fraas, 1867 from the Schilfsandstein (Stuttgart Formation, lower Carnian, Upper Triassic) of Stuttgart, Germany". Neues Jahrbuch für Geologie und Paläontologie - Abhandlungen. 267 (3): 353–362. doi:10.1127/0077-7749/2013/0317.
  4. 1 2 3 4 5 6 Martín D. Ezcurra; Lucas E. Fiorelli; Agustín G. Martinelli; Sebastián Rocher; M. Belén von Baczko; Miguel Ezpeleta; Jeremías R. A. Taborda; E. Martín Hechenleitner; M. Jimena Trotteyn; Julia B. Desojo (2017). "Deep faunistic turnovers preceded the rise of dinosaurs in southwestern Pangaea". Nature Ecology & Evolution. 1 (10): 1477–1483. Bibcode:2017NatEE...1.1477E. doi:10.1038/s41559-017-0305-5. hdl: 11336/41466 . PMID   29185518. S2CID   256707805.
  5. 1 2 Lacerda, Marcel B.; França, De; G, Marco A.; Schultz, Cesar L. (2018). "A new erpetosuchid (Pseudosuchia, Archosauria) from the Middle–Late Triassic of Southern Brazil". Zoological Journal of the Linnean Society. 184 (3): 804–824. doi:10.1093/zoolinnean/zly008.
  6. Nesbitt, Sterling; Stocker, Michelle; Parker, William; Wood, Thomas; Sidor, Christian; Angielczyk, Kenneth (2018). "The braincase and endocast of Parringtonia gracilis, a Middle Triassic suchian (Archosaur: Pseudosuchia)". Journal of Vertebrate Paleontology. 37 (6 sup1): 122–141. doi:10.1080/02724634.2017.1393431. S2CID   89657063.