Turkwel hominid

The Turkwel hominid is an indeterminate genus of hominid that lived in Kenya during the Late Pliocene.

## History

A pedal element, the associated partial hand and mandibular fragments with teeth were discovered from south Turkwel river in 1990 by a multinational team brought ran by the National Museums of Kenya. Their association suggests an age of 3.5 million years from the Nachukui Formation, which is broadly contemporaneous with the Hadar Formation of Laetoli. Ward et al. (1999), the original describers, listed the remains as *Australopithecus* sp. in a faunal chart.

## Description

The hand and pedal bones are comparable with *Praeanthropus afarensis*, but they are not the same. The M2/M3 junction in KNM-WT 22944 A is 30 and 40 in the maximum, which the authors note as interesting. The large canines of some *Praeanthropus afarensis* specimens are similarly sized to KNM-WT 22936. No specific identification can be made, yet they resemble earlier non-robust australopithecines. The musculature in the arms was heavy yet the hand skeleton and feet bear evidence of habitual bipedalism rather than knuckle walking. However, the morphology in African apes that knuckle walk is variable and knuckle walking and the fossils show no adaptations for knuckle walking, but this does not exclude the possibility. The functional capabilities and load handling in the hand was similar to non-robust australopiths but differed from *"Australopithecus" anamensis*. Hand suspension and climbing adaptations are also absent in the hand and wrist. The hamulus is large, only comparable in size to Neanderthals, which suggests heavy forelimb musculature; musculature is not necessarily indicative of climbing but rather for powerful gripping, further evidenced by the rotation capacity of the hamate-MC5 joint. The flexor carpi ulnaris was more (functionally) apelike. This would have allowed for certain types of precision gripping based on the suggested rotary capacity of the MC2, with the expanded MC2-capitate area suggested to be a derived feature in hominids caused by selection for gripping.

## Paleoecology

The Turkwell hominids may have been contemporaneous with *Praeanthropus afarensis*, a widespread species at the time. Additionally, *P. afarensis* was from the Hadar Formation, which is roughly overlapping. The Turkwell hominids are from the Nachukui Formation north of the road that runs from Lodwar to Lothagam. The site preserves rodents, lagomorphs, other non-human primates, canids, saber-toothed cats, proboscideans, horses, rhinoceroses, pigs and various artiodactyls.

## Notable Specimens

* KNM-WT 22936: Fragment of the right of a juvenile mandible with a small alveolar clivus near the midline, exposing the root of the permanent right lateral incisor (which is splintered in a section).
* KNM-WT 22944: Associated crania and postcrania.
	+ KNM-WT 22944 A: A right mandibular body with distal M2 and M3 roots visible. However, it is very eroded and of little value for anatomical detail.
	+ KNM-WT 22944 B: A very worn fragmented right mandibular canine crown and root.
	+ KNM-WT 22944 C: An LP3 with measurements that may have been distorted by weathering.
	+ KNM-WT 22944 D: A root with a tiny bit of enamel on the labial side. It may be a lower canine if the crown is broken. Matrix obscures the distal of the root, making it of little anatomical value.
	+ KNM-WT 22944 E: An incomplete tooth, surrounding bone and matrix. Some enamel remains on the very worn occlusal, which is blocked by matrix.
	+ KNM-WT 22944 F: An LI2 with some of the pulp cavity exposed at the upper and lower ends.
	+ KNM-WT 22944 G: Distal 1/1 of the left metacarpal (MC3, probably) that is somewhat damaged.
	+ KNM-WT 22944 H: A left capitate that is complete aside for an abrasion around the margins.
	+ KNM-WT 22944 I: A left hamate that is well preserved except for an abrasion on the dorsal surface.
	+ KNM-WT 22944 J: A left lunate that is well preserved except for a bone spall on the palmar side
	+ KNM-WT 22944 K: Roughly the proximal of the proximal pedal phalanx.

## References

* https://www.sciencedirect.com/science/article/abs/pii/S0047248498902627
* https://doi.org/10.1002/evan.20335