Liliensternus

• Kingdom: Animalia
• Phylum: Chordata
• Class: Reptilia
• Order: Saurischia
• Family: disputed (basal neotheropod)
• Genus:Liliensternus
• Species:Liliensternus liliensternii

Introduction

Liliensternus was a large predatory dinosaur that lived in Late Triassic Europe, primarily in modern day France and Germany. The animal may have been one of the dominant predators in its environment, preying on herbivorous dinosaurs and a variety of prehistoric reptiles, which dominated the terrestrial environment until the end of the Triassic.

In the Triassic period, the continents of the earth were united in a single land mass known as Pangaea. Connections between the continents allowed species to spread widely across the landscape, limited only by geographic barriers like mountains, deserts, and bodies of water. A massive inland sea, the Tethys Seaway, bordered Europe, Africa, and Asia.

Dinosaurs first appeared in the Triassic and rapidly spread throughout the supercontinent. Liliensternus was part of a successful group of predators that dominated the Triassic world. As Pangaea split through tectonic activity, giving rise to the separate supercontinents Gondwana and Laurasia, dinosaur groups were divided into isolated populations that gave rise to a wide variety of unique species.

Classification

Scientists use two primary methods to organize organisms into different groups. Traditional Linnaean taxonomy, also called “systematics,” groups organisms in a hierarchical fashion according to overall physical similarity, while an alternate system called cladistics attempts to create groups that better reflect the evolutionary relationships between species.

Within the Linnaean system, dinosaurs have traditionally been divided into two orders based on pelvic structure: Saurischia, or “lizard-hipped,” and Ornithischia, or "bird-hipped." (While in the twenty-first century some researchers challenged this longstanding division, it remained in wide use.) Liliensternus is considered a saurischian, and further placed in the suborder Theropoda, made up of bipedal predatory dinosaurs. It was initially thought to be part of the Halticosauridae family, and in fact was originally named Halticosaurus liliensterni, but that grouping was later considered dubious and the genus Liliensternus was established in the 1980s.

Cladistic analysis also places Liliensternus in the theropod clade, and more specifically into the Neotheropoda group that proved highly successful and diverse. Further classification of Liliensternus is subject to considerable debate, as it is considered quite basal among neotheropods. Some analyses place it in the basal clade Coelophysoidea, a lineage that had characteristic developments of the skull, hand, and leg bones. Coelophysids all had narrow skulls with distinct fenestrae, or skull openings that both reduced the weight of the skull and added strength. Some classifications further place Liliensternus in the clade Coelophysidae (also recognized as a family in Linnaean taxonomy), though many researchers consider it outside this group.

Anatomy

Liliensternus was a relatively large predator, reaching between 5 and 6 meters (16.4–20 ft) in length and standing nearly 2.7 meters (almost 9 ft) at the hip. Paleontologists estimate that adult Liliensternus may have weighed between 127–500 kilograms (280–1,000 lbs).

Like all theropods, Liliensternus had longer rear legs, which were well muscled and ended in clawed feet. The forelimbs were shorter but still robust, and the hands had five fingers, with the middle three digits longer than the other two. The fingers were long and graceful and ended in sharp claws.

Liliensternus had a long, stiffened tail, most likely used to balance the animal when running. The neck was long and flexible, and the animal had a tapering snout lined with recurved sharp teeth. The top of the skull is believed to have featured a bony crest similar to Dilophosaurus, the function of which remains unknown.

Paleontologists have no direct evidence to suggest what type of skin Liliensternus had, but it may have had pebbled scales, similar to skin impressions found for other dinosaurs. Though the animal's coloration is unknown, Liliensternus was predatory and appeared in landscape that was partially forested, making it likely that the animal was cryptically colored to enhance its predatory effectiveness.

Intelligence

Scientists have estimated animal intelligence through a measurement known as the encephalization quotient (EQ), which is based on a brain size to body size ratio. Although no specific EQ has been measured for Liliensternus, theropods in general are believed to have had the highest ratings among dinosaurs. (Predators are generally higher in intelligence than herbivores, allowing them an advantage over their potential prey.) Members of the clade Coelophysoidea had narrow skulls compared to later theropods, so they may have been slightly less intelligent. Still, Liliensternus and its relatives were probably among the more intelligent animals living in the Late Triassic.

Reproduction and Population

Scientists know little about the reproductive behavior of Liliensternus. The animal was most likely oviparous, meaning that it reproduced by laying eggs. Paleontologists believe that many large dinosaurs were too heavy to incubate their eggs by sitting on the nest and therefore covered the nest in vegetation to protect the eggs from temperature fluctuations.

Liliensternus is known from only a few specimens, and paleontologists believe that the animal was uncommon within its range. Paleontologists are also uncertain whether male and female Liliensternus were identical or whether there were physical differences separating the sexes.

Diet

Liliensternus was a carnivore, judging by its anatomy, and may have preyed on a variety of species, including herbivorous dinosaurs and prehistoric reptiles. In addition to large prey, Liliensternus may have been opportunistic, feeding on smaller amphibians and reptiles, and possibly scavenging from carcasses.

Behavior

There is no evidence to suggest that Liliensternus displayed any social behavior. Paleontologists have found groups of coelophysid fossils in some areas, indicating that relatives of Liliensternus at least occasionally congregated into groups. Some paleontologists believe that coelophysids did not travel or hunt cooperatively but, rather, sometimes congregated around a shared food source.

Habitat and Other Life Forms

In the Late Triassic, Europe was warmer than in the modern era, covered in a patchwork of forests, flood plains, and vast desert regions. Gymnosperms, like conifers and cycads, were the dominant form of vegetation and the first modern conifers, many resembling modern evergreens, were spreading across the landscape. Angiosperms, or flowering plants, wouldn’t emerge until the Cretaceous.

The dicynodonts, large herbivorous therapsids, were one of the dominant terrestrial vertebrate lineages in the Triassic, along with several other groups of large prehistoric reptiles. Late Triassic Europe also had a variety of herbivorous dinosaurs including Plateosaurus and Ruelia, both related to the large sauropod dinosaurs that proliferated during the Jurassic.

In addition to Liliensternus, there were a number of other predatory species in Triassic Europe, including the theropod hunter Velocipes and the small predator Procompsognathus. During the Late Triassic, a variety of crocodylomorphs, ancestors of modern crocodiles and alligators, also hunted alongside the predatory dinosaurs. The small species Saltoposuchus is known from remains found in Europe.

Research

The first Liliensternus specimen was described by paleontologist Friedrich von Huene in 1934, from a specimen uncovered in Germany. The species was initially called Halticosaurus liliensternus. Paleontologist Samuel P. Welles later created the genus Liliensternus to separate the species from another Halticosaurus species found in Europe, and the Halticosaurus largely fell out of use. The name Lilensternus comes from the last name of amateur paleontologist Hugo Rühle von Lilienstern.

Cladistic analyses later placed Liliensternus in or near the coelophysid group. A second species of Liliensternus besides Liliensternus liliensternii was proposed in the 1990s, but was reclassified as Lophostropheus in the 2000s. Liliensternus is known only from a few incomplete, sub-adult specimens, and therefore many details including the full size of the species remains unknown. Further research has focused on classification, with most researchers agreeing on placement of the genus as a basal neotheropod.

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