Procompsognathus

Kingdom: Animalia

Phylum: Chordata

Class: Reptilia

Order: Saurischia

Family: Coelophysidae

Genus: Procompsognathus

Species: Procompsognathus triassicus

Introduction

Procompsognathus was a small predatory dinosaur that lived in the Late Triassic forests and scrub plains of what is now Germany and England. The dinosaur has typically been identified as one of the earliest members of the theropods, the dominant lineage of predatory dinosaurs throughout the Mesozoic.

In the Triassic period, the continents of the earth were united in a single land mass called Pangaea. The first dinosaurs evolved during this period and spread across the world. During the Jurassic and Cretaceous, the continents split apart under the influence of tectonic movement. Following this, the major groups of dinosaurs radiated into distinct northern and southern faunas.

Procompsognathus emerged alongside a number of other primitive theropods in the Triassic and lived in a world still populated by the lineages of prehistoric amphibians and reptiles that had dominated in the Permian period (299–251 million years ago). Procompsognathus and other early theropods spread across the globe and diversified into a staggering array of predators that dominated the terrestrial environment throughout the Cretaceous.

Classification

Scientists have long used two primary methods to classify organisms into different groups. The traditional Linnaean taxonomy, or “systematics,” groups organisms hierarchically according to overall physical similarity, while an alternate system called “cladistics” creates groups called “clades” in an effort to reconstruct the evolutionary relationships between species.

The Linnaean system places Procompsognathus within the order Saurischia, because of the “lizard-like” orientation of its pelvis. From there, the species is generally placed into the suborder Theropoda, bipedal dinosaurs that were primarily predatory. Because the limited specimen originally found of Procompsognathus was in poor condition and incomplete, debates about its exact classification continued into the first decades of the twenty-first century. While it had initially been suggested that the Procompsognathus should be placed within its own family, it was suggested upon later analyses that, due to certain anatomical characteristics, it should belong to the family Coelophysidae, which includes other primitive theropods like Coelophysis. However, some researchers also criticized this placement.

Cladistic analysis also typically uses the clade Theropoda, defined partially by a reduction in the number of fingers to four or less and the presence of a furcula or “wishbone.” From there, the animal is placed into the clade Coelophysoidea, a group of relatively primitive predators that had not yet evolved the advanced skull and limb features that would become characteristic of later theropods.

Anatomy

Procompsognathus was a small dinosaur, measuring about 1.2 meters (3.9 ft) including its tail, and weighing approximately 1 kilogram (2.2 lbs). The dinosaur had long rear legs ending in three-toed, clawed feet. The arms were significantly smaller, with sharp grasping claws on the hands.

Procompsognathus has an unusual skull, which some paleontologists believed placed the animal among the non-dinosaurian crocodylomorph group, partially due to the poor condition of the fossils discovered. The skull was relatively long, with a tapered snout and jaws lined with sharp, recurved teeth. Triassic Europe was a patchwork of forests, scrub, and floodplains, and Procompsognathus was likely cryptically colored, allowing the animal to blend into its environment.

Intelligence

Paleontologist James A. Hopson used the ratio of brain to body mass, called the encephalization quotient (EQ), to estimate the intelligence of certain groups of dinosaurs. Hopson found that while most dinosaurs fell into a range of 0.1 to 2.0, a few dinosaurs had EQ ratings as high as 5.8, making them similar in intelligence to some small mammalian predators. The EQ scale has an upper limit of 8.0, the approximate value calculated for the human brain.

On average, dinosaurs were less intelligent than most modern mammals and birds, but paleontologists believe that the dinosaurs may have had an advantage in intelligence over the prehistoric reptiles that preceded them. Though an EQ rating has not been calculated for Procompsognathus, the theropod dinosaurs are generally considered to have been among the most intelligent dinosaur groups.

Reproduction and Population

As Procompsognathus is known from only a small number of incomplete specimens, paleontologists are also uncertain about the animal's reproductive behavior. It is likely that Procompsognathus was oviparous, as eggs have been found for many groups of dinosaurs that evolved in the Jurassic and Cretaceous. Later theropod species laid nests of up to ten eggs.

There is additional evidence to suggest that some theropods sat on their nests to brood their eggs like modern birds. Other species may have covered their shallow nests with vegetation for insulation, as seen with crocodiles. Paleontologists also have little information regarding the population size of Procompsognathus. As the species is known from limited specimens, it may have existed in small populations and may have been rare throughout its range.

Diet

Procompsognathus was most likely a predator and probably specialized in capturing insects, small reptiles, and amphibians. Fossils have been uncovered from Triassic beds in Europe, indicating that there was a diverse fauna of small animals that might have fallen prey to dinosaurian predators like Procompsognathus.

Some paleontologists have speculated that small predatory dinosaurs like Procompsognathus may have occasionally fed on fish from inland streams and rivers. Paleontologists have found coprolites from species typically believed to be related, like Coelophysis, containing the remnants of what appears to be fish. Procompsognathus specimens were uncovered from environments that were once arid scrub, indicating that the species may not have ventured as close to open water as some of its relatives.

Behavior

There is evidence to suggest that some theropods gathered into groups. Paleontologists have found fossilized footprints indicating groups of theropods travelling together. Other fossil sites have revealed concentrations of predators like Coelophysis grouped around larger herbivorous dinosaurs, which some believe indicates cooperative hunting. There is no direct evidence to suggest that Procompsognathus travelled or gathered in groups. Considering the animal's size, it may have lived as a solitary predator or in mated pairs.

Habitat and Other Life Forms

Late Triassic Germany contained a variety of environments, from low flood plains to vast upland scrub plains. Specialists studying the paleobotany of the Late Triassic have found that the era marks the dominance of gymnosperms like the “true conifers,” as plants from the genus Neocalamites, shrubby plants that dominated in the Early Triassic, were becoming less common. There were also a wide variety of small reptiles and amphibians in the Late Triassic, including the first-known genus of turtle.

The dicynodonts, a group of reptiles that dominated the terrestrial environment, were in decline by the Late Triassic. The sauropodomorph group, which would become the most dominant group of herbivorous dinosaurs in the Jurassic, appeared in the Triassic with one of the largest animals of the period, the early sauropodomorph Plateosaurus.

In addition to Procompsognathus, there were a variety of other predators in the environment, including the large theropod Liliensternus and the slightly larger Halticosaurus. A variety of predatory crocodylomorphs, early relatives of crocodiles, competed with early dinosaurs for the spot as top predators.

Research

The initial specimen of Procompsognathus was named in 1914 by paleontologist Eberhard Fraas from a specimen discovered in the Keuper Formation in the area that is now Wurttemberg, Germany. Paleontologist Friedrich von Huene added another specimen in 1921.

Paleontologists John Ostrom and Paul Sereno later suggested that Procompsognathus should not be placed in the theropod group, but multiple studies in 2003, 2005, and 2006 suggested that the animal was properly located within the theropod clade, based largely on features of the spinal column and skull.

Bibliography

Briggs, Derek E. G., and Peter R. Crowther. Paleobiology II. Wiley-Blackwell, 2001.

Carpenter, Kenneth. Eggs, Nests and Baby Dinosaurs: A Look at Dinosaur Reproduction. Indiana UP, 1999.

Chinsamay-Turan, Anusuya. Microstructure of Dinosaur Bone: Deciphering Biology with Fine-Scale Techniques. Johns Hopkins UP, 2005.

Farlow, James O., et al. “Theropod Locomotion.” Integrative and Comparative Biology, vol. 40, 2000, pp. 640–63.

Fastovsky, David E., and David B. Weishampel. Dinosaurs: A Concise Natural History. 3rd ed., Cambridge UP, 2016.

Fastovsky, David E., and David B. Weishampel. Evolution and Extinction of the Dinosaurs. 2nd ed., Cambridge UP, 2007.

Horner, Jack, and James Gorman. How to Build a Dinosaur: Extinction Doesn’t Have to Be Forever. Dutton, 2009.

Horner, John R., and Edwin Dobb. Dinosaur Lives: Unearthing an Evolutionary Saga. Mariner Books, 1998.

Lucas, Spencer G. Dinosaurs: The Textbook. 6th ed., Columbia UP, 2016.

Martin, Anthony J. Introduction to the Study of Dinosaurs. 2nd ed., Blackwell, 2006.

"Meet the Ceratosauria." University of California Museum of Paleontology, www.ucmp.berkeley.edu/diapsids/saurischia/ceratosauria.html. Accessed June 2010.

Paul, Gregory S. The Princeton Field Guide to Dinosaurs. 2nd ed., Princeton UP, 2016.

"Procompsognathus." Natural History Museum, www.nhm.ac.uk/discover/dino-directory/procompsognathus.html. Accessed 29 Apr. 2020.

Sereno, Paul C. “The Evolution of Dinosaurs.” Science, vol. 284, 1999, p. 2137.

Sereno, P. C., and R. Wild. “Procompsognathus: Theropod, ‘Thecodont’ or Both?” Journal of Vertebrate Paleontology, vol. 12, 1992, pp. 435–58.

Weishampel, David B., et al., editors. The Dinosauria. 2nd ed., U of California P, 2004.