Procompsognathus: a genus of theropod dinosaur

Procompsognatus (lat.: Procompsognathus) is a genus of theropod dinosaurs of the Compsognathid family (lat.: Compsognathidae), lived in the territory of modern Northern Europe (in particular, in Germany) at the end of the Triassic period, approximately 210 million years ago. It is assumed that this genus was represented by a single species Procompsognathus triassicus. It was a small “bipedal” carnivorous dinosaur of light build.

The generic name Procompsognathus is translated into Russian as “the ancestor of the graceful jaw” and is derived from the name of a also small, but later predatory dinosaur (who lived on Earth at the end of the Jurassic period) Compsognathus (Compsognathus; “graceful jaw”). The specific name triassicus means that the dinosaur belongs to the Triassic geological period.

Procompsognatus: description

Procompsognathus could have reached 1 meter in length, although in 1913 the German paleontologist Eberhard Fraas estimated its body length at 75 cm. In 2010, American researcher Gregory Scott Paul suggested that the dinosaur’s body weight was 1 kg.

This theropod had long hind and short forelimbs, large hands with claws, a long narrow snout with jaws studded with many small teeth, and a stiff tail. The length of the found femur of the holotype of this genus is 93 mm, and the length of the tibia is 112 mm.

The tibia of procompsognathus is approximately 20% longer than the femur, which is the result of an adaptation closely related to the development of running techniques in dinosaurs, which suggests that these theropods were good runners.

Location of the find and its description

A fragmentary and poorly preserved skeleton of Procompsognathus was discovered in the middle stratum of the Löwenstein Sandstone Formation (Germ.: Löwenstein) in the Weißer Steinbruch quarry, owned by Albert Burrer and located near the town of Pfaffenheim in Baden-Württemberg, Germany.

Albert Burrer found dinosaur bones in the spring of 1909 in deposits of white sandstone and blue-gray argillaceous limestone, which belong to the Norian stage of the Triassic period and were formed about 210 million years ago.

The holotype No. SMNS 12591 consisted of bone fragments imprinted in 3 pieces of sandstone: the first of them preserved a small, badly destroyed skull only 7 cm long with a lower jaw.

The second and third pieces contained partially articulated skeletal remains, including 29 cervical, lumbar, and tail vertebrae; elements of the shoulder girdle and one forelimb; ilium; both pubic bones and hind limbs. The holotype was the skeletal remains of an adult.

Burrer sent the fossils to the director of the Stuttgart Royal Museum of Natural History Eberhard Fraas. On October 9, 1911, at one of his lectures, Fraas named this holotype “Hallopus celerrimus”, mistaking it for the remains of a jumping dinosaur species (lat.: celerrimus = “fastest-footed”), belonging to the genus Hallopus (a genus of small ancient crocodiles), whose representatives had a body only about 60 cm long, and classified this species as the ancestor of birds.

However, later, in an official publication, the scientist decided to use a different name for it. In 1913 he named this species Procompsognathus triassicus. The dinosaur holotype is kept in the collection of the State Museum of Natural History in Stuttgart, Germany.

In 1921, the German paleontologist Friedrich von Huene added two more dinosaurs to the genus Procompsognatus, the bones of which were also found in the Burrera quarry in 1908. We are talking about specimen no. SMNS 12352, which includes part of the skull and lower jaw of a specimen larger than the holotype, and specimen no. SMNS 12352a, represented by only one left hand.

Procompsognaths lived in a relatively arid, inland environment and could feed on insects, lizards, and other small prey. Contemporaries of this genus of dinosaurs were coelophysoids (lat.: Coelophysoida) Halticosaurus (Halticosaurus) and Dolichosaurus (Dolichosaurus), as well as sauropodomorphs Plateosaurus (Plateosaurus gracilis species) and Ephraasia (Efraasia minor species).

In 2004, a team of scientists led by American paleontologist David Weishampel noted that traces of theropods and fossils of an unnamed genus of dinosaurs from the family Herrerasaurids (lat.: Herrerasauridae).

Holotype # SMNS 12591 (former SMNS 12352) indicates that Procompsognatus was clearly a small bipedal carnivore, but the extremely poor condition of the remains of the only known specimen makes it difficult to accurately identify them. Fraas originally assigned Procompsognatus to the superorder Dinosaurs (lat.: Dinosauria). In 1923, the Hungarian paleontologist Franz Nopcza (Hungarian.: Franz Nopcsa) ranked him among the family of “Procompsognathins” invented by him (lat.: Procompsognathinae), and von Huene in 1929 to the Procompsognathids family he singled out, although today both of these classifications are rarely used.

In 1932, Friedrich von Huene included Procompsognatus in the non-dinosaur suborder Pseudosuchia. However, since then, almost all scientists consider the “ancestor of the graceful jaw” to be a theropod dinosaur. In 1992, the American Paul Sereno and the German Rupert Wild stated that the holotype of Procompsognatus consisted of fossils of two different animals: the skeleton without a skull belonged, in their opinion, to a theropod, possibly a coelophysoid related to Segisaurus , and the skull and specimens of the remains described by Friedrich von Huene, they considered the bones of the basal crocodiloma salto-pozuha (a species of Saltoposuchus connectens).

However, in 1993, Sankar Chatterjee continued the study and, according to its results, refuted their assumption and attributed the skull to Teropode, similar to Sintars, or Megapnosaus, and also showed that this could not be crocodilomorph, since it did not have no crocodilomorph, since it did not have no crocodile Distinctive features inherent in this group of dinosaurs. Sereno (in 1997) and Argentines Martin Escurra (Spanish).: Martin Ezcurra) with Fernando Novas (in 2007) conducted a phylogenetic analysis, the results of which confirmed the correctness of the theory that Procompsognatus belongs to the family Coelophysidae (Coelophysidae). This genus may have been most closely related to Segisaurus (a species of Segisaurus halli).

The classification of instances No. SMNS 12352 and No. SMNS 12352a proposed by Friedrich von Huene caused a lot of controversy. So, in 1982, the American paleontologist John Ostrom (Eng.: John Ostrom) stated that specimens no. SMNS 12352 and no. SMNS 12352a belong to a member of a different taxon than the holotype described above. In 2006 and 2008, the Paleontologist Fabien Knoll (Fabien Knoll) came to the conclusion that the copy of the remains of the remains of the SMNS 12352 is a crocodilomorph, and the copy No. SMNS 12352A is also a crocodilomorph or some other basal archosaurus.

In her opinion, the skullless skeleton, to which she assigned accession number SMNS 12591, belongs to a member of the superfamily Coelophysoid; and the skull, henceforth numbered SMNS 12591a, is part of a skeleton, possibly a later, derived theropod, perhaps some basal tetanur. In 2012, after performing an axial computed tomography, Knoll reconfirmed that specimen # SMNS 12352 was a crocodylomorph remains, but, as she determined, did not belong to a saltotype.

In 2002, Oliver Rauhut and Axel Hungerbuhler noted features of the dinosaur’s vertebrae that suggest that Procompsognathus could be a member of the Coelophyside family or the infraorder Ceratosaurus (lat.: Cratosauria), and in 2005 a group of scientists, led by Matthew Carrano) conducted a second study of the remains of a related procompsonom of the segizaur and found that both of these kinds belonged to the family of cellsida within the outfit dinosaur. In 2004, the American David Allen came to the conclusion that Procompsognathus was a non-dinosaur primitive representative of the ornithodire reptiles (Ornithodira).

In addition, an analysis was made of the anatomical features of procompsognatus, the totality of which distinguishes it from all other animals. At the same time, it turned out that some, although not all, of the analyzed features are simultaneously autapomorphic, i.e.,.e. unique to this genus. So, in 2000, Rauhut noted that the scapula in procompsognatus is narrower than in the genus Coelophysis (species Coelophysis bauri).

In 1998, Shankar Chatterjee stated that the skull of Procompsognatus shares a number of common derived (synapomorphic) features common to all theropods, including:

  • the presence of an additional maxillary window;
  • vomers fused in the rostral part and considerably elongated towards the internal nares;
  • the presence of a transverse posthustle process of latterosfenoid;
  • The fused orbitospenoids.
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