Delotrochanter is an extinct genus of large-sized carnivoran mammals, belonging to the Amphicyonidae ("bear dogs"), that lived in the Great Plains of North America during the Oligocene to Early Miocene.
A pair of damaged lower jaws (CM 1603) and associated remains were found by Olaf Peterson in May 1904 in the Pine Ridge escarpment near the head of Warbonnet Creek, Nebraska.
Despite being the first temnocyonines discovered in the Great Plains, Peterson's lack of familiarity led him to identify them as an indeterminate canid (during this time amphicyonids were classified as members of the dog family).
Loomis never described the fossil, and it was damaged when it was pressed into a wall of wet plaster at the Amherst College Museum, and was first described by Mildred Schlain in 1980 in an unpublished master study.
Most impressively, a crushed skull (UNSM 47800) and associated postcranial remains were discovered in a den at Beardog Hill, alongside numerous specimens of Daphoenodon superbus.
[1] Paul Miller discovered fragmented lower jaws and isolated upper teeth belonging to Delotrochanter major near Van Tassell in 1927.
[1] Its dentition was durophagous and adapted towards crushing, differing from Mammacyon by the proportions of its carnassial-molar battery, with its blunt-cusped cheek teeth being unlike those of any canid or hyaena.
The massive fourth premolar possesses a short metastylar blade, which forms a moderately developed shear surface with the large paracone.
The first molar possesses a vertical shear surface, which is not quite as developed as in large species of Temnocyon, and is formed by the lingual faces of the paracone and metacone.
Their long and slender femur is slightly curved in the sagittal plane, similar to a wolf, but its the femoral head and neck are almost at a right angle to the diaphysis.
It is part of a late Oligocene radiation, which resulted in the emergence of large hypercarnivores (Temnocyon) and durophages (Mammacyon and Delotrochanter) in the Great Plains.
Interestingly, this postdates the extinction of Mammacyon ferocior, suggesting that large Delotrochanter only emerged after the disappearance of this big, durophagous temnocyonine.
Their deep jaws, strong mandibular symphysis, and canines showcase the strength and leverage of their bite, while their rather blunt carnassials and broad molars allowed them to crush and grind hard food items.
D. oryktes has values between large cats and spotted hyaenas in both these areas, suggesting strong resistance to forces applied at the symphysis.
[1] The smaller size and more gracile build of the geologically younger specimen of D. oryktes suggests that it was female, and that there was notable sexual dimorphism within the species.
The evolution of denning behaviour likely represents an adaption to the emergence of open grasslands, as pups need to be concealed and protected, while the adults pursued prey over large distances.
Among them is the similar sized Daphoenodon superbus, which had a wolf like detention, and was also capable of cracking bone, even if it lacked the durophagous adaptions of Delotrochanter.
Other animals found here include Ysengrinia, a lion-sized amphicyonid of Eurasian origin, and the giant chalicothere Moropus, as well as the huge entelodont Daeodon.
[5] These omnivores also possessed durophagous adaptions, but their much larger size indicates that they were able to process carcasses of big herbivores much more easily than Delotrochanter could.