Schultzsuchus
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''Schultzsuchus'' is an extinct genus of
pseudosuchian Pseudosuchia, from Ancient Greek ψεύδος (''pseúdos)'', meaning "false", and σούχος (''soúkhos''), meaning "crocodile" is one of two major divisions of Archosauria, including living crocodilians and all archosaurs more closely relat ...
from the
Triassic The Triassic ( ; sometimes symbolized 🝈) is a geologic period and system which spans 50.5 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.4 Mya. The Triassic is t ...
Santa Maria Formation The Santa Maria Formation is a sedimentary rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, " rauisuchian" pseudosuchians, and early dinosaurs and othe ...
of
Brazil Brazil, officially the Federative Republic of Brazil, is the largest country in South America. It is the world's List of countries and dependencies by area, fifth-largest country by area and the List of countries and dependencies by population ...
. Initially described as a species of ''
Prestosuchus ''Prestosuchus'' (meaning "Prestes crocodile") is an extinct genus of pseudosuchian in the group Loricata, which also includes ''Saurosuchus'' and ''Postosuchus''. It has historically been referred to as a "rauisuchian", and was the defining mem ...
'', a 2024 study found the
taxon In biology, a taxon (back-formation from ''taxonomy''; : taxa) is a group of one or more populations of an organism or organisms seen by taxonomists to form a unit. Although neither is required, a taxon is usually known by a particular name and ...
to differ in multiple aspects of its anatomy, enough to warrant it being placed in a distinct
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
. Unlike ''
Prestosuchus ''Prestosuchus'' (meaning "Prestes crocodile") is an extinct genus of pseudosuchian in the group Loricata, which also includes ''Saurosuchus'' and ''Postosuchus''. It has historically been referred to as a "rauisuchian", and was the defining mem ...
'', which is a more derived member of
Loricata Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as ''Postosuchus'' and ''Prestosuchus''. More specifically, Loricata includes Crocodylomorpha (the persistent archosaur subset which ...
, ''Schultzsuchus'' appears to have been a basal member of the
clade In biology, a clade (), also known as a Monophyly, monophyletic group or natural group, is a group of organisms that is composed of a common ancestor and all of its descendants. Clades are the fundamental unit of cladistics, a modern approach t ...
Poposauroidea Poposauroidea is a clade of advanced Pseudosuchian, pseudosuchians. It includes poposaurids, Shuvosaurinae, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as ''Qianosuchus'' and ''Lotosaurus''. It excludes most large predato ...
.


History and naming

The remains of what is now called ''Schultzsuchus'' were first described under the name ''Prestosuchus loricatus'' by German paleontologist
Friedrich von Huene Baron Friedrich Richard von Hoyningen-Huene (22 March 1875 – 4 April 1969) was a German nobleman paleontologist who described a large number of dinosaurs, more than anyone else in 20th-century Europe. He studied a range of Permo-Carbonife ...
in 1938,von Huene, F. (1938). Die fossilen Reptilien des südamerikanischen Gondwanalandes. Ergebnisse der Sauriergrabungen in Südbrasilien 1928/29. ''Neues Jahrbuch für Mineralogie, Geologie Und Paläontologie'', 1938(3), 142–151. who had recovered the fossils of this pseudosuchian from the Cynodontier Sanga of the
Santa Maria Supersequence The Santa Maria Formation is a sedimentary geological formation, rock formation found in Rio Grande do Sul, Brazil. It is primarily Carnian in age (Late Triassic), and is notable for its fossils of cynodonts, "rauisuchian" pseudosuchians, and ear ...
in 1928/29 and regarded the animal as having been congeneric with ''Prestosuchus chiniquensis'', also named by him. While '' Prestosuchus chiniquensis'' saw several additional finds attributed to it over the years, making it one of the best understood early pseudosuchians, ''P. loricatus'' received much less attention. This was in part due to the nature of the material, which consisted of a singular tooth crown, some vertebrae, elements of the hindlimbs as well as osteoderms. In 1942 von Huene tentatively referred some additional vertebrae and a
calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...
to this taxon, but he himself was uncertain of this assessment.von Huene, F. (1942). ''Die fossilen Reptilien des südamerikanischen Gondwanalandes''. C.H. Beck'sche Verlagsbuchhandlung. The validity of ''P. loricatus'' eventually came into question, with several authors regarding this a possibility. Krebs (1976) and Barberena (1978) regarded the species to have probably been synonymous with ''P. chiniquensis'', though Krebs remarked that a comprehensive study of the type material was required to tell for sure.Krebs, B. (1976). Pseudosuchia. In O. Kuhn (Ed.), ''Handbuch der Paläoherpetologie. Teil 13: Thecodontia'' (pp. 40–98). Gustav-Fischer-Verlag, München. Parrish (1993) seemed to follow this interpretation as well, combining material of both species interchangeably when scoring it for a
phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...
. Kischlat went further by arguing that the type material of ''P. loricatus'' actually belonged to two different animals, which he named ''Karamuru vorax'' and ''Abaporu loricatus''. However, these names are regarded as somewhat problematic, as ''Abaporu loricatus'' was only mentioned a single time with no other occurrences of the name within the same publication. Furthermore, no formal proposition of a new generic name was made, no holotype was proposed and even the given specimen number is noted for being flawed according to Desojo and Rauhut. Ultimately, both '' Karamuru'' and ''Abaporu'' are regarded as
nomina nuda Nomen may refer to: *Nomen gentilicium, the middle part of Ancient Roman names ** ''Nomen est omen'', a Latin quote about nominative determinism *Nomen (ancient Egypt), the personal name of Ancient Egyptian pharaohs *Jaume Nomen (born 1960), Catal ...
. A thorough examination of the type material of ''Prestosuchus loricatus'' was eventually published by Desojo and Rauhut in 2024, who agreed with Kischlat (2023) in so far that the material did represent a taxon distinct from ''Prestosuchus'', which they dubbed ''Schultzsuchus''. ''Schultzsuchus'' was named in honor of Cesar Schultz, who was noted for his contributions to the understanding of the vertebrate fauna of the Santa Maria Supersequence.


Description

''Schultzsuchus'' is only known from limited material thought to have belonged to a single individual, though this is sometimes called into question. Among the material are the tip of a tooth, the
neural arch Each vertebra (: vertebrae) is an irregular bone with a complex structure composed of bone and some hyaline cartilage, that make up the vertebral column or spine, of vertebrates. The proportions of the vertebrae differ according to their spinal ...
of the axis vertebra, three additional neural arches of the neck vertebrae (one of which complete), partial cervical and dorsal
rib In vertebrate anatomy, ribs () are the long curved bones which form the rib cage, part of the axial skeleton. In most tetrapods, ribs surround the thoracic cavity, enabling the lungs to expand and thus facilitate breathing by expanding the ...
s, four tail vertebrae and the neural arch and neural spine of two more. Fossils of the hindlimbs are also known, namely both
ischia Ischia ( , , ) is a volcanic island in the Tyrrhenian Sea. It lies at the northern end of the Gulf of Naples, about from the city of Naples. It is the largest of the Phlegrean Islands. Although inhabited since the Bronze Age, as a Ancient G ...
still in articulation, a single
calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...
and a few
metatarsals The metatarsal bones or metatarsus (: metatarsi) are a group of five long bones in the midfoot, located between the tarsal bones (which form the heel and the ankle) and the phalanges (toes). Lacking individual names, the metatarsal bones are nu ...
. Finally, several
osteoderms Osteoderms are bony deposits forming scales, plates, or other structures based in the dermis. Osteoderms are found in many groups of Extant taxon, extant and extinct reptiles and amphibians, including lizards, crocodilians, frogs, Temnospondyli, ...
have also been described for this taxon. The only known skull remains of ''Schultzsuchus'' consist of a single tooth crown. The element is conical in shape and stout, but with laterally compressed sides and
carinae ''Carinae'' was an area of ancient Rome. It was one of its most exclusive neighborhoods, where many of the senatorial class lived. Florus described the ''Carinae'' as the "''most celebrated part of the city''" (''celeberrima pars urbis''). Desc ...
that feature partially abraded serrations ( ziphodont). The tooth is recurved, causing the mesial carina to be convex in shape, while the carina facing towards the back of the jaw is straight. The only carina well-enough preserved to show the amount of serrations is the mesial carina, which has about 10 denticles across , which is only slightly lower than the amount seen in '' Heptasuchus''. There has been some doubt on the assignment of the tooth to ''Schultzsuchus'' given the fact that it's an isolated element not directly associated with any other material while also having been found with the fossils of a synapsid. However, the shape does suggest that it belonged to what was likely a paracrocodylomorph or some other predatory archosaur. A notable feature that distinguishes ''Schultzsuchus'' from ''Prestosuchus'' is the fact that the cervical vertebrae preserve
epipophyses Epipophyses are bony projections of the cervical vertebrae found in archosauromorphs, particularly dinosaurs (including some basal birds). These paired processes sit above the postzygapophyses on the rear of the vertebral neural arch. Their m ...
, which are generally absent from pseudosuchians bar some exceptions. Desojo and Rauhut describe the epipophyses of ''Schultzsuchus'' as being high ridges that are clearly set apart from the postzygapophysis that they protrude from, anatomy best matched by ''
Revueltosaurus ''Revueltosaurus'' ("Revuelto lizard") is an extinct genus of suchian pseudosuchian from Late Triassic (late Carnian to middle Norian stage) deposits of New Mexico, Arizona and North Carolina, United States. Many specimens, mostly teeth, have bee ...
'' (a stem-aetosaur),
dinosaurs Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutio ...
, '' Stagonosuchus'', ''
Rauisuchus ''Rauisuchus'' (meaning "Wilhelm Rau's crocodile") is a genus of extinct archosaurs which lived in what is now the Geopark of Paleorrota (Santa María Formation), Brazil, during the Triassic, Late Triassic period (235–228 million years ago). It ...
'' and '' Postosuchus alisonae''. Similarly, an epipophysis is also present on the second neck vertebra, the axis, which is even less common and stated to be present in ''Revueltosaurus'', '' Longosuchus'', ''
Xilousuchus ''Xilousuchus'' is an extinct genus of poposauroid from lower Triassic (Olenekian stage) deposits of Fugu County of northeastern Shanxi Province, China. Xilousuchus is one of the oldest archosaurs known to date. Discovery and naming It is ...
'' and possibly '' Effigia''. The neural spine of the neck vertebrae also represents a markedly different anatomy from ''Prestosuchus'' and most other basal loricatans. In those forms the neural spine tends to be short from the front to the back and tall, keeping a relatively consistent rectangular profile and being notably thickened. ''Schultzsuchus'' meanwhile has neural spines is visibly longer anteroposteriorly and shaped like a fan, owing to the spinous process expanding towards the top most edge of the bone. Even more so than the presence of epipophysis, this element could suggest affinities with poposauroids, as Desojo and Rauhut note that the only other pseudosuchians with such neural spines are ''Xilousuchus'', '' Qianosuchus'', ''
Arizonasaurus ''Arizonasaurus'' (meaning "Arizona reptile") was a ctenosauriscid archosaur from the Middle Triassic (243 million years ago) Moenkopi Formation of what is now Arizona. The taxon is known for having a large back sail formed by elongated neural sp ...
'' and '' Mandasuchus'', all of which appeared as poposauroids in their 2024 publication on ''Schultzsuchus''. The elongated neural arches might indicate that ''Schultzsuchus'' had elongated neck vertebrae, a notion that might find additional support in the presence of just such a vertebra from the type locality. While this bone was originally assigned to a
saurischian Saurischia ( , meaning "reptile-hipped" from the Greek ' () meaning 'lizard' and ' () meaning 'hip joint') is one of the two basic divisions of dinosaurs (the other being Ornithischia), classified by their hip structure. Saurischia and Ornithis ...
, its anatomy is similar to that of a poposauroid, with some taxa within this group even having elongated necks. Though Desojo and Rauhut do not concretely assign the vertebrae to ''Schultzsuchus'', further study could change that. The
ischium The ischium (; : is ...
, of which both elements are preserved in articulation, preserves a large pit on the surface where the bones would articulate with the ilium. Such a pit is absent in ''Prestosuchus'' and seen in some, but not all, poposauroids. ''Schultzsuchus'' also lacks the longitudinal depression that is found across the shaft of most early Loricatan ischia and is thus considered a
synapomorphy In phylogenetics, an apomorphy (or derived trait) is a novel Phenotypic trait, character or character state that has evolution, evolved from its ancestral form (or Plesiomorphy and symplesiomorphy, plesiomorphy). A synapomorphy is an apomorphy sh ...
of the clade by Desojo and Rauhut. The
calcaneum In humans and many other primates, the calcaneus (; from the Latin ''calcaneus'' or ''calcaneum'', meaning heel; : calcanei or calcanea) or heel bone is a bone of the tarsus of the foot which constitutes the heel. In some other animals, it is t ...
, the heel bone, of ''Schultzsuchus'' has a tuber that is much higher than it is broad, which is the exact opposite of ''Prestosuchus'', in which the tuber is broader than it is high. Both did possess a pit in the underside of the tuber, but it is noted as being much shallower in ''Schultzsuchus''.


Phylogeny

Several
phylogenetic analysis In biology, phylogenetics () is the study of the evolutionary history of life using observable characteristics of organisms (or genes), which is known as phylogenetic inference. It infers the relationship among organisms based on empirical data ...
were run to determine the position of ''Schultzsuchus'' among pseudosuchians, yielding some results that stand in stark contrast to the position of ''Prestosuchus''. Both the equally weighted and implied weighted suggest that ''Schultzsuchus'' was not a prestosuchid but rather an early diverging member of the clade
Poposauroidea Poposauroidea is a clade of advanced Pseudosuchian, pseudosuchians. It includes poposaurids, Shuvosaurinae, shuvosaurids, ctenosauriscids, and other unusual pseudosuchians such as ''Qianosuchus'' and ''Lotosaurus''. It excludes most large predato ...
. '' Mandasuchus'' and '' Mambawakale'' were also derived as poposauroids in more basal positions than ''Schultzsuchus'', but according to Desojo and Rauhut it would only take a few steps for either of them to be recovered within
Loricata Loricata is a clade of archosaur reptiles that includes crocodilians and some of their Triassic relatives, such as ''Postosuchus'' and ''Prestosuchus''. More specifically, Loricata includes Crocodylomorpha (the persistent archosaur subset which ...
. ''Schultzsuchus'' meanwhile was recovered as the
sister taxon In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and ...
of '' Qianosuchus'' and all more derived poposauroids (consisting of Poposauridae, Shuvosauridae, ''
Lotosaurus ''Lotosaurus'' is an extinct genus of sail-backed poposauroid known from Hunan Province of central China. Discovery ''Lotosaurus'' is known from the holotype IVPP V 4881 (or possibly V 4880), an articulated and well-preserved s ...
'' and
Ctenosauriscidae Ctenosauriscidae is an extinct family of pseudosuchian archosaurs within the clade Poposauroidea. Ctenosauriscids existed in Africa, Asia, Europe and North America during the Early Triassic to the Middle Triassic period (latest Olenekian to Anisi ...
). This is primarily based on two anatomical characters shared with poposauroids (both relating to the neck vertebrae) and the absence of traits seen in the derived members of the clade. The only analysis that fail to recover these results are those with higher weighing strengths, which instead place ''Schultzsuchus'' as being placed in a more derived position than ''Saurosuchus'' towards the crown of Pseudosuchia.


References

{{taxonbar, from1=Q124515504, from2=Q124515514 Paracrocodylomorpha Late Triassic pseudosuchians Ladinian genera Late Triassic reptiles of South America Triassic Brazil Fossils of Brazil Santa Maria Formation Fossil taxa described in 2024 Prehistoric pseudosuchian genera