Fossil elephant cranium reveals key adaptations that enabled its species
to thrive as grasslands spread across eastern Africa

Date:
November 9, 2021
Source:
University of Michigan
Summary:
A remarkably well-preserved fossil elephant cranium from Kenya is
helping scientists understand how its species became the dominant
elephant in eastern Africa several million years ago, a time when
a cooler, drier climate allowed grasslands to spread and when
habitually bipedal human ancestors first appeared on the landscape.



FULL STORY ==========================================================================
A remarkably well-preserved fossil elephant cranium from Kenya is helping scientists understand how its species became the dominant elephant in
eastern Africa several million years ago, a time when a cooler, drier
climate allowed grasslands to spread and when habitually bipedal human ancestors first appeared on the landscape.


========================================================================== Dated to 4.5 million years ago and recovered from a site on the
northeast side of Lake Turkana, it is the only well-preserved elephant
cranium -- the portion of the skull that encloses the brain -- from that
time. It isabout 85% intact and holds a wealth of previously unavailable anatomical detail, according to University of Michigan paleontologist
William Sanders.

Known by its museum number, KNM-ER 63642, the roughly 2-ton cranium
belonged to a massive adult male of the species Loxodonta adaurora,
an extinct evolutionary cousin of modern African elephants but not a
direct ancestor.

KNM-ER 63642 is both impressively immense and unexpectedly modern in
aspect, displaying adaptations that likely gave L. adaurora an edge
when competing with other large mammals for grasses, according to
Sanders, lead author of a study published online Oct. 21 in the journal Palaeovertebrata. Co-authors include Meave and Louise Leakey, who led
the recovery effort and who are best known for the discovery of early
hominid specimens and artifacts from Lake Turkana and elsewhere.

The L. adaurora cranium is striking because it is raised and compressed
from front to back, suggesting a novel alignment of chewing muscles
well-suited for the efficient shearing of grasses. In addition, the
animal's molars are higher- crowned and had thicker coatings of cementum
than other early elephants, making the teeth more resistant to the wear
common in animals that feed on grasses close to the ground.

"The evident synchronization of morphological adaptations and feeding
behavior revealed by this study of Loxodonta adaurora may explain why it
became the dominant elephant species of the early Pliocene," said Sanders,
who has studied fossil elephants and their relatives for nearly 40 years
in Africa and Arabia.



========================================================================== Eastern Africa was home to seven or eight known species of early elephants
at the time, along with horses, antelope, rhinos, pigs and hippos. Many
of these animals were becoming grazers and competing for the available
grasses.

"The adaptations of L. adaurora put it at a great advantage over more
primitive elephants, in that it could probably use less energy to
chew more food and live longer to have more offspring," said Sanders,
associate research scientist at the U-M Museum of Paleontology and in
the Department of Anthropology.

Recovery, conservation, dating, description and identification of the
elephant cranium involved collaborative work between researchers and techniciansfrom the Turkana Basin Institute, National Museums of Kenya, University of Michigan, Rutgers University, Smithsonian Institution and University of Utah.

KNM-ER 63642 was discovered in 2013 by a member of the Koobi Fora Research Project from a single molar that was visible at the surface.

Excavation revealed the presence of a nearly complete cranium. The tusks
and the jawbone were missing, and no other remains from that individual
were recovered. The adult male is estimated to have been 30 to 34 years
old at death.



==========================================================================
The fossilized cranium, together with the plaster jacket that protected it
and some attached sediment, weighed about 2 tons. Based on a previous
study of the skeleton from another L. adaurora adult male with a
similar-sized skull, this individual likely weighed about 9 tons and
probably stood about 12 feet at the shoulder -- bigger than average male elephants of modern times.

"In my opinion, this elephant skull is by far the most impressive specimen
that we have in the Kenyan paleontological collection from Lake Turkana,
both in its completeness and in its size," said paleontologist and study co-author Louise Leakey of the Koobi Fora Research Project. "When the
teeth were seen on the surface, we had no idea that a complete cranium
would be uncovered, and the excavation and recovery operation was both challenging and exciting." KNM-ER 63642 is now permanently housed at
the Turkana Basin Institute's facility in Ileret, Kenya. It is the only well-preserved elephant cranium from the interval beginning with the
origin of elephants 8 million years ago and ending 3.5 million years ago, according to Sanders.

In addition to providing a trove of insights about the anatomy of early elephants, the newly described cranium also deepens our understanding of
the connections between those creatures and our earliest human ancestors,
the habitually bipedal australopithecines.

Loxodonta adaurora and other early elephants coexisted with two well-known australopithecine species in eastern Africa: Australopithecusanamensis, recovered by Meave Leakey in and nearby the Lake Turkana Basin, Kenya,
and A.

afarensis, found at sites in Hadar, Ethiopia, and Laetoli, Tanzania.

In the early Pliocene, as grassy woodlands and grasslands spread across
eastern Africa, the australopithecines would have benefited from the
presence of elephants. The animals' feeding activities helped keep grasses
low to the ground, which would have allowed our upright ancestors to
see over the vegetation and to watch for predators.

Elephants also disrupt closed woodlands and create open areas by
knocking over trees, uprooting shrubs, and trampling paths through dense forest. And they spread nutrients and grass seed in their dung.

"The origins and early successes of our own biological family are tied
to elephants," Sanders said. "Their presence on the landscape created
more open conditions that favored the activities and adaptations of our
first bipedal hominin ancestors.

"From this perspective, it is ironically tragic that current human
activities of encroaching land use, poaching and human-driven climate
change are now threatening the extinction of the mammal lineage that
helped us to begin our own evolutionary journey." The project was funded
by the National Geographic Society; Meave and Louise Leakey are National Geographic Explorers at Large. Additional support was provided by ARTEC
3D, African Fossils and the Turkana Basin Institute. Funding for research travel and site visits by Sanders was provided by the Abu Dhabi Tourism
and Culture Authority, Meave Leakey and the Turkana Basin Institute, and several Scott Turner Grants from the University of Michigan Department
of Earth and Environmental Sciences.

========================================================================== Story Source: Materials provided by University_of_Michigan. Note:
Content may be edited for style and length.


========================================================================== Journal Reference:
1. William Sanders, Meave Leakey, Louise Leakey, Craig Feibel, Timothy
Gichunge Ibui, Cyprian Nyete, Pauline Mbatha, Francis Brown.

Morphological description and identification of an extraordinary
new elephant cranium from the early Pliocene of Ileret, Kenya.

Palaeovertebrata, 2021; 44 (2): e3 DOI: 10.18563/pv.44.2.e3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2021/11/211109120347.htm

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