https://www.sciencedirect.com/science/article/abs/pii/S0047248420301597

Abstract
A partial left femur (TM 266-01-063) was recovered in July 2001 at
Toros-Menalla,
Chad, at the same fossiliferous location as the late Miocene holotype of
Sahelanthropus tchadensis (the cranium TM 266-01-060-1). It was recognized
as a
probable primate femur in 2004 when one of the authors was undertaking
a taphonomic survey of the fossil assemblages from Toros-Menalla.We are
confident
the TM 266 femoral shaft belongs to a hominid. It could sample a hominid
hitherto
unrepresented at Toros-Menalla, but a more parsimonious working hypothesis
is that
it belongs to S. tchadensis. The differences between TM 266 and the late
Miocene
Orrorin tugenensis partial femur BAR 1002000, from Kenya, are consistent with
maintaining at least a species-level distinction between S. tchadensis and O.
tugenensis. The results of our preliminary functional analysis suggest the
TM 266
femoral shaft belongs to an individual that was not habitually bipedal,
something that
should be taken into account when considering the relationships of S.
tchadensis. The
circumstances of its discovery should encourage researchers to check to
see whether
there is more postcranial evidence of S. tchadensis among the fossils
recovered from
Toros-Menalla.

"The size and morphology of the TM 266 femoral shaft are much more
consistent with
it belonging to a fossil hominid than to a fossil monkey. In terms of size
and shape, the
external morphology of the shaft is closer to that of the common
chimpanzee than to
modern humans, gorillas, or orangutans"

"An erect posture and bipedal locomotion have traditionally been accepted
as one of
the defining features of the hominin clade (e.g., Le Gros Clark, 1955),
and they are
routinely used as criteria to assess whether Pliocene hominid fossils
should be included
in the hominin clade (e.g., Haile-Selassie et al., 2004; White et al.,
2009; Simpson, 2013; Pilbeam and Lieberman, 2017). That is not to say that
all habitually bipedal hominids are
necessarily hominins, but the consensus is that to be a member of the
hominin clade,
the morphology of a candidate species needs to be consistent with habitual
bipedalism. If
it could be demonstrated that the morphology of the TM 266 femoral shaft
was consistent with its owner being a habitual biped, this would
strengthen the case for it being a hominin."

"The lack of clear evidence that the TM 266 femur is from a hominid that
was habitually
bipedal further weakens the already weak case (Mongle et al., 2019) for S.
tchadensis being
a stem hominin."

[Edited for readability]

https://www.sciencedirect.com/science/article/abs/pii/S0047248420301597

Abstract
A partial left femur (TM 266-01-063) was recovered in July
2001 at Toros-Menalla, Chad, at the same fossiliferous
location as the late Miocene holotype of Sahelanthropus
tchadensis (the cranium TM 266-01-060-1). It was
recognized as a probable primate femur in 2004 when one
of the authors was undertaking a taphonomic survey of the
fossil assemblages from Toros-Menalla.We are confident
the TM 266 femoral shaft belongs to a hominid. It could
sample a hominid hitherto unrepresented at Toros-Menalla,
but a more parsimonious working hypothesis is that it
belongs to S. tchadensis. The differences between TM 266
and the late Miocene Orrorin tugenensis partial femur BAR
1002000, from Kenya, are consistent with maintaining at
least a species-level distinction between S. tchadensis and
O. tugenensis. The results of our preliminary functional
analysis suggest the TM 266 femoral shaft belongs to an
individual that was not habitually bipedal, something that
should be taken into account when considering the
relationships of S. tchadensis. The circumstances of its
discovery should encourage researchers to check to see
whether there is more postcranial evidence of S. tchadensis
among the fossils recovered from Toros-Menalla.

"The size and morphology of the TM 266 femoral shaft are
much more consistent with it belonging to a fossil hominid
than to a fossil monkey. In terms of size and shape, the
external morphology of the shaft is closer to that of the
common chimpanzee than to modern humans, gorillas, or
orangutans"

"An erect posture and bipedal locomotion have
traditionally been accepted as one of the defining features
of the hominin clade (e.g., Le Gros Clark, 1955), and they
are routinely used as criteria to assess whether Pliocene
hominid fossils should be included in the hominin clade
(e.g., Haile-Selassie et al., 2004; White et al., 2009;
Simpson, 2013; Pilbeam and Lieberman, 2017). That is not
to say that all habitually bipedal hominids are necessarily
hominins, but the consensus is that to be a member of the
hominin clade, the morphology of a candidate species
needs to be consistent with habitual bipedalism. If it could
be demonstrated that the morphology of the TM 266
femoral shaft was consistent with its owner being a
habitual biped, this would strengthen the case for it being a
hominin."

"The lack of clear evidence that the TM 266 femur is from a
hominid that was habitually bipedal further weakens the
already weak case (Mongle et al., 2019) for S. tchadensis
being a stem hominin."