Caphirosaurus

Caphirosaurus Temporal range: Late Cretaceous, 69–66 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Reconstruction of the C. imperator type specimen (FT 4520) at the Venceia Museum of Natural History
Scientific classification
Type species
†Caphirosaurus imperator d'Everard, 1902
Other species
†C. caesar Jour & Leon, 1925 †C. virilis Balvini et al, 1973
Synonyms
Genus synonymy Imperatorsaurus Jour & Leon, 1925 Urceonychus James, 1961 Caphirodylus Balvini et al, 1973 Terrorsaurus Cape, 1992

Caphirosaurus is a genus of caphirosaurid theropod dinosaur. The species Caphirosaurus imperator (imperator meaning "emperor" in Latin), sometimes colloquially called Imperatorsaurus, is one of the best represented of the large theropods. Caphirosaurus lived throughout what is now Caphiria and southern Urcea, on what was then a supercontinent known as Sarpolevantia. Caphirosaurus had a much wider range than other theropods. Fossils are found in a variety of rock formations dating to the Upper Cretaceous period, 69 to 66 million years ago. It was the last known member of the caphirosaurids and among the last non-avian dinosaurs to exist before the Cretaceous–Paleogene extinction event.

Like other caphirosaurids, Caphirosaurus was a bipedal carnivore with a massive skull balanced by a long, heavy tail. Relative to its large and powerful hind limbs, the forelimbs of Caphirosaurus were short but unusually powerful for their size, and they had two clawed digits. The most complete specimen measures up to 14.1 meters (47 feet) in length, though C. imperator could grow to lengths of over 15.2 m (50 ft), up to 4.25 m (14 ft) tall at the hips, and according to most modern estimates 8.4 metric tons (9.3 short tons) to 14 metric tons (15.4 short tons) in weight. Although a few other theropods rivaled or exceeded Caphirosaurus imperator in size, it is still among the largest known land predators and is estimated to have exerted the strongest bite force among all terrestrial animals. By far the largest carnivore in its environment, Caphirosaurus imperator was most likely an apex predator, preying upon hadrosaurs, juvenile armored herbivores like Tassellasaurus and Testudosaurus, and possibly sauropods. Some experts have suggested the dinosaur was primarily a scavenger. The question of whether Caphirosaurus was an apex predator or a pure scavenger was among the longest debates in paleontology. Most paleontologists today accept that Caphirosaurus was both an active predator and a scavenger.

Specimens of Caphirosaurus imperator include some that are nearly complete skeletons, and soft tissue and proteins have been reported in at least two specimens. The abundance of fossil material has allowed significant research into many aspects of its biology, including its life history and biomechanics. The feeding habits, physiology, and potential speed of Caphirosaurus imperator are a few subjects of debate. As the archetypal theropod, Caphirosaurus has been one of the best-known dinosaurs since the early 20th century and has been featured in film, advertising, postal stamps, and many other media.

Description

Skeletal reconstruction of C. imperator

C. imperator was one of the largest land carnivores of all time. One of the largest and the most complete specimens, nicknamed Panthera (PNTR IN3031), measured 14.1 meters (47 feet) long, was 3.99 meters (13 ft) tall at the hips, and according to the most recent studies, using a variety of techniques, estimated to have weighed between 8.4 metric tons (9.3 short tons) to 14 metric tons (15.4 short tons). A specimen nicknamed Aurelius (FNK 1942), located at the Urceopolis Natural History Museum, is reported to measure 15.2 m (50 ft) in length. Using a mass estimation technique that extrapolates from the circumference of the femur, Aurelius was estimated as the largest known specimen at 8.8 metric tons (9.7 short tons) in weight.

The largest known C. imperator skull is 1.52 meters (5 ft) in length. Large fenestrae (openings) in the skull reduced weight, as in all carnivorous theropods. In other respects Caphirosaurus' skull was significantly different from those of large non-caphirosaurid theropods. It was extremely wide at the rear but had a narrow snout, allowing unusually good binocular vision. The skull bones were massive and the nasals and some other bones were fused, preventing movement between them; but many were pneumatized (contained a "honeycomb" of tiny air spaces) and thus lighter. These and other skull-strengthening features are part of the caphirosaurid trend towards an increasingly powerful bite, which easily surpassed that of all non-caphirosaurids. The tip of the upper jaw was U-shaped (most non-caphirosaurid carnivores had V-shaped upper jaws), which increased the amount of tissue and bone a Caphirosaurus could rip out with one bite, although it also increased the stresses on the front teeth.

The shoulder girdle was longer than the entire forelimb. The shoulder blade had a narrow shaft but was exceptionally expanded at its upper end. It connected via a long forward protrusion to the coracoid, which was rounded. Both shoulder blades were connected by a small furcula. The paired breast bones possibly were made of cartilage only. The forelimb or arm was very short. The upper arm bone, the humerus, was short but robust. It had a narrow upper end with an exceptionally rounded head. The lower arm bones, the ulna and radius, were straight elements, much shorter than the humerus. The second metacarpal was longer and wider than the first, whereas normally in theropods the opposite is true. The forelimbs had only two clawed fingers, along with an additional splint-like small third metacarpal representing the remnant of a third digit.

In contrast to the arms, the hindlimbs were among the longest in proportion to body size of any theropod. In the foot, the metatarsus was "arctometatarsalian", meaning that the part of the third metatarsal near the ankle was pinched. The third metatarsal was also exceptionally sinuous. Compensating for the immense bulk of the animal, many bones throughout the skeleton were hollowed, reducing its weight without significant loss of strength.

Discovery and history

Lower jaw of C. imperator excavated by d'Everard's expedition in 1902

Cleo (FJ 8823) displayed in Collinebourg Natural History Museum

Teeth from what is now documented as a Caphirosaurus imperator were found in 1874 by Thibault d'Avignon near Serracene, Meceria. In the early 1890s, Krinkos collected postcranial elements in eastern Belactrum. Phillipe d'Everard found the first partial skeleton of C. imperator in eastern Belctrum in 1900. d'Everard found another partial skeleton in Serracene in 1902, comprising approximately 36 fossilized bones. Writing at the time d'Everard said "Quarry No. 1 contains the lower jaw, femur, pubes, humerus, three vertebrae and two undetermined bones of a large Carnivorous Dinosaur not described by d'Avignon... I have never seen anything like it from the Cretaceous". The generic name is derived from the name of the country in which it was discovered, Caphiria, and the Greek word σαῦρος (sauros, meaning "lizard"). d'Everard used the Latin word imperator, meaning "emperor", for the specific name. The full binomial therefore translates to "Caphirian lizard emperor" or "Emperor Lizard of Caphiria", emphasizing the animal's size and perceived dominance over other species of the time.

An expedition to Cesindes by paleontologist duo Jour & Leon in 1925 uncovered another partial skeleton, about 25% complete. Initially described as a new genus with the name Imperatorsaurus, it was soon recognized as a subspecies of Caphirosaurus and given the name C. caesar. The Great War prevented any further paleontological expeditions to be mounted in Caphiria.

Post-Great War

Beginning in the late 1950s there was renewed interest in Caphirosaurus, resulting in the recovery of 42 skeletons (5–80% complete by bone count) from Caphiria. In 1961, Urcean paleontologist Dr. William James located and recovered the partial skeleton named "JAB 007" in southern Urcea. JAB 007 is 15% complete by bone count including a complete skull. It was initially described as a new species with the scientific name Urceonychus jamesi, but was since recognized as a C. imperator.

A new subspecies, C. virilis, was discovered in 1973 by Caphiric amateur paleontologist Balvini. Aided by volunteers and the University of Caphiria, the 90% complete skeleton dubbed Juliette (JBD 2402) was excavated and brought back the University of Caphiria for study. The species of the skeleton was the topic of dispute for years to come. The specimen was initially described as Caphirodylus balvini, while others, notably Yonderian sauropod specialist C.G. Kier thought it to be a juvenile C. imperator. It was widely recognized as a junveile C. imperator until Johann Fürster, upon close examination and study, in 2001 suggested that it may be a seperate subspecies entirely. Another two C. virilis have since been excavated, in 2008 and 2015.

The 1990s saw numerous discoveries of C. imperator, with nearly twice as many finds as in all previous years, including two of the most complete skeletons found to date, Cleo (FJ 8823) and Vito (FE 2412), both more than 92% complete. A study of FJ 8823's fossilized bones showed that Cleo reached full size at age 19 and died at the age of 28, the longest estimated life of any Caphirosaurus known. Cleo had many bone pathologies, including broken and healed ribs, a broken (and healed) neck, and a substantial hole in the back of its head, about the size of a Caphirosaurus tooth.

Paleobiology

Profile wiev of the skull of Vito (FE 2412)

Over half of the known C. imperator specimens appear to have died within six years of reaching sexual maturity, a pattern which is also seen in other sauroppods and in some large, long-lived birds and mammals today. These species are characterized by high infant mortality rates, followed by relatively low mortality among juveniles. Mortality increases again following sexual maturity, partly due to the stresses of reproduction. One study suggests that the rarity of juvenile C. imperator fossils is due in part to low juvenile mortality rates; the animals were not dying in large numbers at these ages, and thus were not often fossilized. This rarity may also be due to the incompleteness of the fossil record or to the bias of fossil collectors towards larger, more spectacular specimens. In a 2013 lecture, Johann Fürster suggested that dinosaurs "lived fast and died young" because they reproduced quickly whereas mammals have long life spans because they take longer to reproduce. Fürster also suggested that Caphirosaurus reproduced quickly and died young, but attributes their short life spans to the dangerous lives they lived.

A study conducted by the University of Collinebourg found that Caphirosaurus had heightened sensory abilities, highlighting relatively rapid and coordinated eye and head movements; an enhanced ability to sense low frequency sounds, which would allow Caphirosaurus to track prey movements from long distances; and an enhanced sense of smell. A study published by Pierre concluded that Caphirosaurus had keen vision. By applying modified perimetry to facial reconstructions of several dinosaurs including Caphirosaurus, the study found that Caphirosaurus had a binocular range of 55 degrees, surpassing that of modern hawks. Pierre estimated that Caphirosaurus had 13 times the visual acuity of a human and surpassed the visual acuity of an eagle, which is 3.6 times that of a person. Stevens estimated a limiting far point (that is, the distance at which an object can be seen as separate from the horizon) as far as 6 km (3.7 mi) away, which is greater than the 1.6 km (1 mi) that a human can see.

Most paleontologists accept that Caphirosaurus was both an active predator and a scavenger like most large carnivores. By far the largest carnivore in its environment, C. imperator was most likely an apex predator, preying upon hadrosaurs, juvenile armored herbivores like Tassellasaurus and Testudosaurus, and possibly sauropods. A study in 2012 by Francois de Carre and Edmond Falk found that Caphirosaurus had the most powerful bite of any terrestrial animal that has ever lived, finding an adult Caphirosaurus could have exerted 35,000 to 57,000 N (7,868 to 12,814 lbf) of force in the back teeth. Even higher estimates were made by Falk in 2003. This allowed it to crush bones during repetitive biting and fully consume the carcasses of large dinosaurs. Falk and colleagues calculated that Caphirosaurus was capable of a maximum jaw gape of around 80 degrees, a necessary adaptation for a wide range of jaw angles to power the creature's strong bite.

See also

• History of paleontology