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Boverisuchus/sandbox Temporal range:
Ysengrinia americana skull at Agate Fossil Beds National Monument
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Carnivora
Family:	†Amphicyonidae
Subfamily:	†Thaumastocyoninae
Genus:	†Ysengrinia Ginsburg (1965)
Species
Ysengrinia americana Ysengrinia depereti Ysengrinia geraniana Ysengrinia tolosana Ysengrinia valentiana

Ysengrinia is an extinct genus of carnivoran in the family Amphicyonidae, which lived in Europe, Asia, and North America during the Early Miocene.

History

In 1998, the species Ysengrinia ginsburgi was erected on the basis of fossils discovered at the locality Arrisdrift in Namibia, which would have made it the only species of the genus known from Africa. However, newer studies have recognized the distinct anatomical differences between this taxon and the type species Y. gerandiana, resulting in the creation of the separate genus Namibiocyon for the amphicyonid from Arrisdrift. Similarly, a tooth from the Askazansor Formation in Kazakhstan previously referred to Ysengrinia has since been moved to the genus Askazansoria.

Species

Y. americana

Y. americana is known from late Arikareean-aged rocks from Wyoming and Nebraska. The first fossils belonging to this species, an upper canine and a calcaneum, were discovered by H.C. Clifford in 1875, and used as holotype for the description of “Amphicyon” americanus by Wortman in 1901. Several more fossils were found in the decades afterwards, but it was not until 1972 that Hunt first proposed the presence of Ysengrinia in North America. Hunt then assigned “Amphicyon” americanus to the genus in 2002, resulting in the new combination Ysengrinia americana. He furthermore designated F:AM 54147, the only complete skull known of this genus, which was discovered in 1937 in the Anderson Ranch Formation, as its paratype.

Description

• short legs, robust

Phylogeny

Restoration of Ysengrinia

Ysengrinia seems to have been rare throughout its range; most fossils are isolated teeth and jaw or skull fragments. Material from outside North America is usually referred to Y. ginsburgi, though other species have been proposed; the fragmentary nature of the fossils and possible variation within species makes any identification at the species level difficult. The most complete fossils have been found in North America, so descriptions of the living animal are based on the North American Y. americana.

Several studies have suggested that Ysengrinia is polyphyletic. Cladistic analysis recovers “Ysengrinia” americana to be outside the group that includes the rest of the genus, while “Ysengrinia” valentiana is more closely related to Thaumastocyon than to the type species Ysengrinia gerandia. It is also pointed out that Y. americana has notable differences in the upper dentition compared to the rest of the genus, and displays a morphotype less adapted to hypercarnivory. Ysengrinia tolosana and Ysengrinia depereti, only known from their lower dentition, were not included in the analysis, and are in an uncertain systematic position. Y. gerandia and “Y.” valentiana both belong to the Thaumastocyoninae, while “Y.” americana may either be the sister taxon of that subfamily, or be more closely related to Amphicyonines.

Below is the cladogram based on cranial, mandibular and dental characters, after Morales et al., 2021:

	Pseudocyonopsis landesquei
	Daphoenodon superbus Cynelos lemanensis "Ysengrinia" americana Thaumastocyoninae Crassidia intermedia Ysengrinia gerandia Peignecyon felinoides Tomocyon grivensis "Ysengrinia" valentiana Agnotherium antiquum Ammitocyon kainos Thaumastocyon bourgeoisi Thaumastocyon dirus

Fossils from Arrisdrift in Namibia and Moghra in Egypt have also been referred to this genus as Ysengrinia ginsburgi. This, however, has been rejected since, although the actual genera to which these fossils belong has been a topic of debate. Morlo et al. (2019) allocated the material from Arrisdrift to the genus Cynelos, as C. ginsburgi, and created the new species Cynelos anubisi for the one from Egypt. Morales et al. (2016) first referred Y. ginsburgi to the genus Afrocyon, but a later study by the same lead author erected the new genera Namibiocyon and Mogharacyon for the two taxa.

Paleoecology

Earliest europe:

Distribution

After the local extinction of both nimravids and hyaenodonts, the temnocyonine amphicyonids were the only large-sized carnivorans present on the North American continent near the Oligocene-Miocene boundary. However, during the earliest Miocene, tectonic activities in Asia led to a dispersal event of Eurasian species into North America that lasted from circa 23 to 15.5 Ma, from the late Arikareean to the Hemingfordian. Ysengrinia americana, which was considerably larger than even the largest temnocyonines, was among the earliest of these immigrants, first appearing around 23 Ma, alongside another amphicyonid, Cynelos, chalicothere Moropus, the rhinoceros Menoceras and the ursid Cephalogale. Another amphicyonid, Daphoenodon, first occurred at the same time, though this genus likely descended from earlier amphicyonids endemic to the New World. During this time period, the climate dried, and savannahs spread over the Great Plains, with trees mostly being restricted to riverbanks. Ephermal lakes were often the only source of water available, and mass deaths resulted when they dried out during one of the common droughts. It is in these waterhole deposits that Ysengrinia was found. A notable locality is Beardog Hill, named for the unusually high number of amphicyonid fossils found here. Most of these belong either to Daphoenodon superbus, or the rarer Delotrochanter oryktes, a temnocyonine showcasing adaptions towards both durophagy and cursoriality, which were found in the remnants of their dens. Other carnivorans found here include two small canids (Phlaocyon annectens and Cormocyon), a small mustelid (Promartes olcotti) and the large, wolverine-like Megalictis simplicidens. Various prey animals dragged to the dens, including oreodont Merychyus and the camels Stenomylus and Oxydactylus, were also discovered. Ysengrinia, however, was not found in the dens, likely as a result of its large size, but only at the waterhole, where Moropus, Menoceras and the huge, omnivorous Daeodon are the most commonly found taxons. Ysengrinia americana was generally associated with waterholes and riparian habitats across its range. In the somewhat younger localities of the Anderson Ranch Formation (formerly known as Upper Harrison Formation), which date to the latest Arikareean, Ysengrinia occurs alongside the youngest known temnocyonines, Temnocyon macrogenys and Delotrochanter major, the Daphoenines Daphoenodon falkenbachi and Adilophontes brachykolos, as well as the immense Megalictis ferox. The following Arikareean-Hemingfordian is characterized by a faunal turnover, which included the disappearance of all afromentioned carnivorans, including Y. americana and temnocyonines, as well as the appearance of several more Eurasian immigrants, among them the earliest North American members of the genus Amphicyon, which first occurred around 18.8 Ma. However, at least some of these sudden extinctions and appearances may be the result of the changing depositional environments, as the Anderson Ranch Formation was accumulated in a semi-arid grassland, whereas the Runningwater Formation was formed by fluvial environments. While Ysengrinia has also been reported from New Mexico, Hunt's review of the American fossils of the genus states that remains of this taxon are restricted to Nebraska and Wyoming.

An upper molar discovered in the Japanese Orematsu Formation, which dates to 16.3-15.6 Ma, has also previously been referred to this genus. Other authors have pointed out that this fossil is notably younger than the youngest known Ysengrinia fossils, and is morphologically similar to that of Cynelos idoneus, a taxon that is furthermore of similar age to the fossil from Japan. A partially preserved maxilla and isolated teeth of Ysengrinia have also been reported from the Xiejahe Fauna of China, which is part of the Shanwang Formation, and dates to circa 18 Ma.