The origin and evolution of Cynodontia (Synapsida, Therapsida): Reassessment of the phylogeny and systematics of the earliest members of this clade using 3D‐imaging technologies
The Anatomical Record,
Journal Year:
2024,
Volume and Issue:
307(4), P. 1634 - 1730
Published: March 5, 2024
Abstract
The
origin
of
cynodonts,
the
group
ancestral
to
and
including
mammals,
is
one
major
outstanding
problems
in
therapsid
evolution.
One
most
troubling
aspects
cynodont
fossil
record
lengthy
Permian
ghost
lineage
between
latest
possible
divergence
from
its
sister
Therocephalia
first
appearance
definitive
cynodonts
late
Permian.
absence
dominance
therocephalians
middle
strata
has
led
some
workers
argue
that
evolved
within
therocephalians,
rendering
latter
paraphyletic,
but
more
recent
analyses
support
reciprocal
monophyly
Cynodontia
Therocephalia.
Furthermore,
although
a
fundamental
dichotomy
derived
subclade
Eucynodontia
well‐supported
phylogeny,
relationships
stemward
Early
Triassic
are
unresolved.
Here,
we
provide
re‐evaluation
phylogeny
Eutheriodontia
(Cynodontia
+
Therocephalia)
an
assessment
character
evolution
group.
Using
computed
tomographic
data
extensive
sampling
earliest
known
(late
Triassic)
selected
exemplars
later
(Middle
onwards)
describe
novel
endocranial
anatomy
these
animals.
These
were
incorporated
into
new
phylogenetic
set
comprehensive
sample
early
cynodonts.
Our
results
previously
recovered
by
other
authors,
recover
as
paraphyletic
with
regards
eutherocephalians
forming
clade
exclusion
“basal
therocephalian”
families
Lycosuchidae
Scylacosauridae.
Though
both
conservatism
homoplasy
mark
non‐mammalian
able
identify
several
synapomorphies
for
eutheriodont
subclades
generally
better‐supported
topologies
than
previous
using
primarily
external
craniodental
characters.
Language: Английский
Endocranial anatomy of the early prozostrodonts (Eucynodontia: Probainognathia) and the neurosensory evolution in mammal forerunners
The Anatomical Record,
Journal Year:
2023,
Volume and Issue:
307(4), P. 1442 - 1473
Published: April 5, 2023
Abstract
Prozostrodon
brasiliensis
and
Therioherpeton
cargnini
are
non‐mammaliaform
cynodonts
that
lived
~233
million
years
ago
(late
Carnian,
Late
Triassic)
in
western
Gondwana.
They
represent
some
of
the
earliest
divergent
members
clade
Prozostrodontia,
which
includes
“tritheledontids”,
tritylodontids,
“brasilodontids”,
mammaliaforms
(including
Mammalia
as
crown
group).
Here,
we
studied
endocranial
anatomy
(cranial
endocast,
nerves,
vessels,
ducts,
ear
region,
nasal
cavity)
these
two
species.
Our
findings
suggest
during
early
prozostrodonts
had
a
brain
with
well‐developed
olfactory
bulbs,
expanded
cerebral
hemispheres
divided
by
interhemispheric
sulcus,
absence
an
unossified
zone
pineal
body.
The
morphology
maxillary
canal
represents
necessary
condition
for
presence
facial
vibrissae.
A
slight
decrease
encephalization
is
observed
at
origin
Prozostrodontia.
This
new
anatomical
information
provides
evidence
evolution
traits
first
prozotrodonts,
Triassic
lineage
culminated
mammals.
Language: Английский
Synchrotron X‐ray micro‐computed tomography enhances our knowledge of the skull anatomy of a Late Triassic ecteniniid cynodont with hypercanines
The Anatomical Record,
Journal Year:
2025,
Volume and Issue:
unknown
Published: Jan. 13, 2025
Abstract
Hypercanines,
or
hypertrophied
canines,
are
observed
in
a
wide
range
of
both
extinct
and
extant
synapsids.
In
non‐mammaliaform
cynodonts,
the
Permo‐Triassic
forerunners
mammals,
long
canines
not
uncommon,
appearing
several
unrelated
taxa
within
clade.
Among
them
is
Trucidocynodon
riograndensis
,
carnivorous
ecteniniid
cynodont
from
Late
Triassic
Brazil,
which
exhibits
specialized
dentition,
including
spear‐shaped
incisors,
very
narrow
sectorial
postcanines
with
distally
oriented
cusps,
all
have
finely
serrated
margins.
Recent
synchrotron
X‐ray
micro‐computed
tomography
large
specimen
(CAPPA/UFSM
0029;
Várzea
do
Agudo
site,
Brazil)
provides
new
insights
into
its
lower
jaw
as
well
offers
first
digital
endocast
an
ecteniniid.
Our
study
reveals
presence
(i)
putatively
opened‐root
adult
stage
possible
unresorbed
remnant
old
canine,
may
indicate
that
stopped
replacing
canines;
(ii)
longer
than
upper
and,
occlusion,
were
kept
inside
deep
paracanine
fossae
perforated
dorsal
surface
rostrum;
(iii)
diastema
between
incisors
absent
holotype;
(iv)
advanced
brain
structures,
such
absence
pineal
body,
cerebral
hemispheres
divided
by
interhemispheric
sulcus
expanded
laterally,
higher
encephalization
quotient
prozostrodonts,
reflecting
homoplastic
evolution
relative
sizes
lineages.
Finally,
abundance
omnivorous
species
at
where
was
found—including
archosauriforms
Dynamosuchus
collisensis
Stenoscelida
aurantiacus
—suggests
diverse
predator
guild
warrants
further
investigation
paleoecological
perspective.
Language: Английский
Revisiting the neuroanatomy of Massetognathus pascuali (Eucynodontia: Cynognathia) from the early Late Triassic of South America using Neutron Tomography
The Science of Nature,
Journal Year:
2025,
Volume and Issue:
112(1)
Published: Jan. 17, 2025
Language: Английский
The fossil record of appendicular muscle evolution in Synapsida on the line to mammals: Part I—Forelimb
The Anatomical Record,
Journal Year:
2023,
Volume and Issue:
307(5), P. 1764 - 1825
Published: Sept. 19, 2023
Abstract
This
paper
is
the
first
in
a
two‐part
series
that
charts
evolution
of
appendicular
musculature
along
mammalian
stem
lineage,
drawing
upon
exceptional
fossil
record
extinct
synapsids.
Here,
attention
focused
on
muscles
forelimb.
Understanding
forelimb
muscular
anatomy
synapsids,
and
how
this
changed
line
to
mammals,
can
provide
important
perspective
for
interpreting
skeletal
functional
diversity
functions
extant
mammals
arose.
study
surveyed
osteological
evidence
attachments
nonmammalian
two
amniote
outgroups,
large
selection
saurians,
salamanders.
Observations
were
integrated
into
an
explicit
phylogenetic
framework,
comprising
73
character–state
complexes
covering
all
crossing
shoulder,
elbow,
wrist
joints.
These
coded
33
operational
taxonomic
units
spanning
>330
Ma
tetrapod
evolution,
ancestral
state
reconstruction
was
used
evaluate
sequence
lineage
from
Amniota
Theria.
In
addition
producing
comprehensive
documentation
muscle
work
has
clarified
homology
hypotheses
across
disparate
taxa
helped
resolve
competing
species.
The
evolutionary
history
complex
nonlinear
narrative,
punctuated
by
multiple
instances
convergence
concentrated
phases
anatomical
transformation.
More
broadly,
highlights
great
insight
fossil‐based
understanding
assembly
novel
body
plans.
Language: Английский
New evidence from high-resolution computed microtomography of Triassic stem-mammal skulls from South America enhances discussions on turbinates before the origin of Mammaliaformes
Scientific Reports,
Journal Year:
2024,
Volume and Issue:
14(1)
Published: June 15, 2024
Abstract
The
nasal
cavity
of
living
mammals
is
a
unique
structural
complex
among
tetrapods,
acquired
along
series
major
morphological
transformations
that
occurred
mainly
during
the
Mesozoic
Era,
within
Synapsida
clade.
Particularly,
non-mammaliaform
cynodonts
document
several
changes
in
skull,
Triassic
Period,
represent
first
steps
mammalian
bauplan.
We
here
explore
five
cynodont
taxa,
namely
Thrinaxodon
,
Chiniquodon
Prozostrodon
Riograndia
and
Brasilodon
order
to
discuss
main
this
skull
region.
did
not
identify
ossified
turbinals
these
taxa
if
present,
as
non-ossified
structures,
they
would
necessarily
be
associated
with
temperature
control
or
development
endothermy.
do,
however,
notice
complexification
cartilage
anchoring
structures
divide
separate
it
from
brain
region
forerunners
mammals.
Language: Английский
Early synapsids neurosensory diversity revealed by CT and synchrotron scanning
The Anatomical Record,
Journal Year:
2024,
Volume and Issue:
unknown
Published: April 10, 2024
Abstract
Non‐mammaliaform
synapsids
(NMS)
represent
the
closest
relatives
of
today's
mammals
among
early
amniotes.
Exploring
their
brain
and
nervous
system
is
key
to
understanding
how
evolved.
Here,
using
CT
Synchrotron
scanning,
we
document
for
first
time
three
extreme
cases
neurosensory
behavioral
adaptations
that
probe
into
wide
range
unexpected
NMS
paleoneurological
diversity.
First,
describe
low‐frequency
hearing
low‐light
conditions
in
non‐mammalian
cynodont
Cistecynodon
parvus
,
supporting
an
obligatory
fossorial
lifestyle.
Second,
uniquely
complex
three‐dimensional
maxillary
canal
morphology
biarmosuchian
Pachydectes
elsi
which
suggests
it
may
have
used
its
cranial
bosses
display
or
low‐energy
combat.
Finally,
introduce
a
paleopathology
found
skull
Moschognathus
whaitsi
.
Since
specimen
was
not
fully
grown,
this
condition
possibility
species
might
engaged
playful
fighting
as
juveniles—a
behavior
both
social
structured.
Additionally,
paper
discusses
other
evidence
could
indicate
tapinocephalid
dinocephalians
were
animals,
living
interacting
closely
with
one
another.
Altogether,
these
examples
diversity
neurological
structures
NMS.
Language: Английский
Micro-CT data reveal new information on the craniomandibular and neuroanatomy of the dicynodont Gordonia (Therapsida: Anomodontia) from the late Permian of Scotland
Zoological Journal of the Linnean Society,
Journal Year:
2024,
Volume and Issue:
unknown
Published: May 1, 2024
Abstract
Dicynodontia
was
an
abundant,
globally
widespread
clade
of
Permo-Triassic
synapsids
on
the
stem
lineage
mammals.
Although
there
is
extensive
body
literature
dicynodont
craniomandibular
anatomy,
only
recently
has
power
computed
tomographic
(CT)
scanning
been
applied
to
this
system.
CT-assisted
research
dicynodonts
focused
smallest
members
clade,
while
larger
(particularly
diverse,
long-ranging
subclade
Bidentalia)
have
received
comparatively
little
attention.
Here,
we
work
towards
filling
that
gap
by
presenting
a
µCT-assisted
reconstruction
‘The
Elgin
Marvel’,
bidentalian
specimen
consisting
complete
cranium
and
mandible
from
late
Permian
deposits
near
Elgin,
Scotland,
which
historically
difficult
study
because
its
unusual
preservation
as
void
space
in
sandstone.
This
can
be
referred
Gordonia,
solely
represented
moulds
specimens.
The
µCT
data
reveal
new
information
palate
endocranium
taxon
could
not
previously
gleaned
physical
made
A
phylogenetic
analysis
indicates
Gordonia
Chinese
Jimusaria
form
bidentalians
characterized
narrow
pterygoid
medial
plates,
expanding
our
understanding
biogeography.
endocast
similar
other
non-cynodont
therapsids,
remarkably
enlarged
pineal
body,
probably
related
exaggeration
sagittal
crest.
Comparisons
encephalization
quotients
(EQ),
measure
brain
size
relative
size,
EQ
most
therapsids.
Language: Английский