Simbakubwa

Simbakubwa Temporal range: 23.0–22.0 Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓ early Miocene
reconstruction of Simbakubwa kutokaafrika
size comparison to human
Scientific classification
Domain:	Eukaryota
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	†Hyaenodonta
Superfamily:	†Hyainailouroidea
Family:	†Hyainailouridae
Subfamily:	†Hyainailourinae
Genus:	†Simbakubwa Borths & Stevens, 2019
Type species
†Simbakubwa kutokaafrika Borths & Stevens, 2019

Simbakubwa ("great lion") is an extinct genus of hyaenodonts to the family Hyainailourinae that lived in Kenya during the early Miocene.^[1]

The fossils of Simbakubwa were first discovered by rural Kenyans at Meswa Bridge, Western Kenya. Thereafter, Matthew Borths and Nancy Stevens published the findings after examining the fossils which had been stored at the Nairobi National Museum in Kenya for decades.^[2] The type specimen consists of a mandible from the lower jaw, a right upper maxilla and some postcranial remains. The light wear patterns on the dentition indicate that the holotype specimen was a young adult at the time of its death.

The name of this genus comes from the Swahili language, meaning "great lion". The species name Simbakubwa kutokaafrika means "great lion of Africa”.

Different regression models produce a wide range of body mass estimates for Simbakubwa kutokaafrika: from a low estimate of 280 kg (620 lb), based on an equation derived from the m3 length of various large carnivorans, comparable to the largest lions, to an upper estimate possibly reaching up to 1,308 and 1,554 kg (2,884 and 3,426 lb), based on equations derived from carnassial length of hyaenodonts and m3 length of felids respectively, which would surpass the modern polar bear in size.^[1] However, hyainailourids possessed proportionally very large heads in comparison to their body, and postcranial remains indicate that the similar sized Hyainailouros was about the size of a tiger, whereas the larger Megistotherium has been estimated to have reached a maximum weight of 500 kilograms (1,100 lb),^[3] though this study estimated the body mass of Megistotherium with a low estimate of 317 kg (699 lb) to higher estimates of 1,794–3,002 kg (3,955–6,618 lb) using the same methods.^[1]

The study of the postcranial remains indicates Simbakubwa was possessed of a semi-digitigrade walking stance.^[1]

Simbakubwa, like other hyainailourids, probably was a specialist hunter and scavenger that preyed on creatures such as rhinoceroses and early proboscideans. It may have been somewhat less specialized in crushing bone than its later relatives such as Hyainailouros. However, like Hyainailouros, Simbakubwa possessed lingually rotating carnassial blades, ensuring a constant shearing edge throughout its life.^[1]