Wednesday, 6 January 2010

What ever happened to Laelaps?

Above; a 19th century reconstruction of Laelaps (centre) from the palaeontologist Edward Cope, featuring in the background other examples of his finds including a Mosasaur on the far right, shown with the forked toungue of a snake. Cope's fascination with the idea of sea serpents is clear in this image and his strong beliefs in relations between serpents and Mosasaurs is valid to this day. Below Laelaps on the bottom left is an outdated reconstruction of the Plesiosaur Elasmosaurus. This shows it with a short neck and long sinuous tail, a condition that was later found to be incorrect by Cope's irritatingly observant rival Marsh. Both did anything to correct and ridicule the other in their battle for scientific credit. Elasmosaurus is now shown to have had a long neck and short tail. Cope was so embarrassed by the mistake that he attempted to obtain every paper he had printed on the creature.

Discovered in 1866 from New Jersey (in eastern North America) were the incomplete remains of a carnivorous theropod dinosaur; a large meat eater belonging to the Tyrannosaur family. This animal is unique for several reasons.

Above; an outdated reconstruction of Laelaps shown on the left hand corner leaping across the plains like a scaly kangaroo with sharp teeth. Since kangaroos were the only modern alalogy to Laelaps during the 19th century many palaeontologists theorised that it lept about, using its tail for balance and as a prop when stood still.

Firstly the location. Dinosaur fossils are relatively rare and incomplete in eastern North America. During the late Cretaceous period at the end of the reign of dinosaurs North America was split into three separate sub continents by an inland sea; one to the north, one to the west and another to the east. The eastern continent; called Appalachia had more lowland areas than the continent to the west. Therefore the environment was probably wetter and more boggy. For some reason dinosaur specimens are relatively insubstantial, perhaps the dinosaurs only inhabited the uplands where deposits rarely preserve fossils. Any that were preserved would be the upland bones that had been bought downhill by streams, getting separated and damaged on the way to be fossilised in the deltas and salt marshes that occupied the lowlands. The dinosaurs of Appalachia had good reason to avoid boggy areas. There were predators like the giant 8 meter long Appalachian croc Deinosuchus. This animal was smaller than the western continent Deinosuchus, but was still a formidable predator. Bite marks on leg bones tell us that it preyed on dinosaurs, even Tyrannosaurs and quite possibly Laelaps as well. In these flowing waters the bones may have become scattered, explaining the lack of complete specimens.
Above; a map of North America about 70 million years ago in the Cretaceous period. On the right is the eastern continent of Appalachia where Laelaps lived. North of Appalachia is the Arctic American continent (Canada) and Greenland.

Above; Deinosuchus was the top predator of dinosaurs in Appalachia, outcompeting Tyrannosaurs such as Laelaps as top predator and forcing them into more insignificant nieches.

Secondly this was the 3rd dinosaur discovered in North America. The specimen was described and named by 19th century palaeontologist Edward Cope. Cope called his find Laelaps aquilinguis (the exact meaning of which I am uncertain due to the conflicting interpretations). The specimen consisted of the leg, arm, a few tail vertebra, some teeth and parts of the skull. Prior to the discovery of Laelaps a bone fragment belonging to the plant eater Hadrosaurus was found very close by. Cope interpreted this as evidence of the Laelaps hunting Hadrosaurus, however I deem this as inconclusive due to Cope's famously vivid imagination and tendency to jump to conclusions. The association is probably a result of coincidence rather than evidence of feeding behaviour in Laelaps.

Above; Laelaps shown in Benjamin Hawkins's painting attacking Hadrosaurus on the left. Probably the influance of Cope's "discovery" of possible hunting behaviour between the two animals due to a Hadrosaur bone fragment found alongside his Laelaps skeleton.

Above; another 19th century reconstruction of Laelaps on the left. The animal is shown kicking a rather ridiculous looking Hadrosaurus. Cope envisioned Laelaps as an animal who's primary weapon consisted of its feet, capable of kick boxing its prey to death like male kangaroos do today.

At first Laelaps was considered to be a relative of Megalosaurus as most meat eating dinosaurs of the time were considered. More recently the animal has been suggested as an unspecific Ceoleurosaur and a Tyrannosaur. In 1997 Ken Carpenter suggested that the animal belonged to its own family due to the combinations of unique and Tyrannosaurian features. Appalachiosaurus, another theropod from eastern USA shares many features with Laelaps, but is classified as a Tyrannosaur. This suggests that Laelaps was a highly derived Tyrannosaur.

Above; the skeleton of Laelaps showing the primitive Tyrannosaurian condition of three fingers rather than two. The slender legs suggests that Laelaps was a fast mover, capable of running down swift prey.

The most visually striking feature is the hand, which supports a huge 8 inch claw. Most Tyrannosaurs had tiny arms that were useless except as balancing aids. To me this is the most obvious non Tyrannosaurian feature. Had Laelaps re-evolved a powerful arm and claws from advanced Tyrannosaur ancestors or was it an early offshoot from the ancestral stock at a stage when the arms were still relatively large in their evolution? The presence of 3 fingers rather than the more advanced condition of 2 fingers suggests that Laelaps was in fact a surviving member of the ancestral Tyrannosaur group. The theory is that Laelaps had become isolated on Appalachia as the more advanced 2 fingered Tyrannosaurs took over from the primitive forms in Asia and western North America. The relatively small size (for a Tyrannosaur of the late Cretaceous) of 5 or 6 meters is another indicator of the primitive affinities of Laelaps.

Above; a modern reconstruction of Laelaps (now called Dryptosaurus). This creature has changed faces several times. First considered to be a kind of Megalosaur it is now thought to be a late surviving member of the primitive Tyrannosaur stock.

So what was the claw for? Most probably an aid in bringing down prey. It could have been a gripping implement for holding victims whilst the teeth did the dirty work. On the western continent the more advanced Tyrannosaurs lost the need for arms altogether, tackling such large prey they used their huge heads to ram and tear apart plant eating dinosaurs. Perhaps Laelaps retained its large arms and small size because it was hunting smaller prey, needing the arms to reach down to the ground and grab small reptiles with the enormous claw. This makes sense when there were much bigger crocodiles lurking about and dominating the post of top predator. Although primarily inhabiting upland areas the Appalachian dinosaurs still needed to come to water for a drink, giving the crocs a chance to kill and a guaranteed supply of meat. In the western continent, however. Upland habitats were more numerous, meaning less crocodiles and more big T'rex's were able to evolve to occupy the neiche of dominant carnivore in the absence of giant crocodiles. This explains the lack of development in eastern Tyrannosaurs as opposed to western ones.

Laelaps was, however short lived. In 1887 Cope's rival Othneil Marsh discovered that the name Laelaps had already been given to a genus of mite. Therefore in the laws of nomenclature Laelaps was renamed Dryptosaurus meaning tear lizard, after the enormous hand claw.
Above; Edward Cope (top) and Othniel Marsh (bottom) were fierce rivals in 19th century American Palaeontology. Both tried to discredit the other in attempts to increase their own scientific credit and appreciation.

In his final days in 1897, being seriously ill Cope was visited by Charels Knite, a renouned boligical artist of his day. Cope advised Knite on how to portray prehistoric life in an article he was illustrating for the Century magazine. One of the many animals portrayed was Laelaps, shown in the painting leaping at another individual as a warm blooded and active animal would do. Later on palaeontologists rejected the idea of dinosaurs being so active. They were reptiles and thus had to be cold blooded and slow moving. In the 1970's and 80's palaeontologist Robert Bakker in his book "The Dinosaur Herisies", published in 1986 attacks the view of dinosaurs as lumbering giants and thus ressurects Cope's and Knite's visions of sprightly dinosaurs. Indeed one of Bakkers beautiful illustrations that accompanies his book shows 2 raptor dinosaurs in exactly the same position as Knite's leaping Laelaps, quite literally stating that the 19th century reconstructions were more accurate than the sluggish ones of the 1960's. More so, this image has made Laelaps one of the more well known dinosaurs, despite the incomplete remains and lack of evidence. It seems that Cope's lively imagination finally paid off, making Laelaps a dinosaur icon for hundreds of years to come.

Above; The leaping Laelaps of Charles Knite (top). This image has become a dinosaur icon, demonstrating the origional view of active and bird like dinosaurs invisioned by Cope was the correct one after all. Since the dinosaur renaissance in the 1970's, plaeontologists realised these animals were not slow moving or cold blooded as was the accepted "fact" of the time, but warm blooded and furry like modern mammals and birds. As a result many recent remakes (bottom) of this painting have been created, showing two Laelaps/Dryptosaurus in the same positions as Knite's image, with body forms anatomically updated and modelled on more recent discoveries and our improved understanding of dinosaur anathomy.

1 comment:

  1. Just to clarify the Elasmosaurus debacle, Joseph Leidy actually pointed it out to Cope that his head was placed on the tail and the body arranged backwards. Cope tried to correct the errors in his publication but acted too hastily and the reprint came out with tons more errors which Marsh then used to embarrass Cope further.