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Morphology and Evolution of Turtles (new book)

From: Ben Creisler

A new book Morphology and Evolution of Turtles, with abstracts and
previews of first few pages posted online. The pdf of the front matter
and table of contents is free:


Lots of Mesozoic stuff. A few highlights and new genera:

Robert L. Carroll (2012)
Problems of the Ancestry of Turtles.
Morphology and Evolution of Turtles. Part 2, 19-36
DOI: 10.1007/978-94-007-4309-0_3

The unquestioned unity of the Chelonia provides a necessary basis for
establishing their interrelationships and determining the evolutionary
history within the group. On the other hand, the host of uniquely
derived features of the oldest known turtles make it extremely
difficult to establish their ancestry among more primitive amniotes.
This is illustrated by the great diversity of taxa that continue to be
proposed as putative sister-taxa of turtles without general acceptance
of any. Nearly every major clade of early amniotes from the late
Paleozoic and early Mesozoic has been proposed as a possible
sister-taxon of turtles, from synapsids to anapsids and diapsids,
including pelycosaurs, captorhinomorphs, procolophonids, pareiasaurs,
aquatic placodonts and crocodiles, but none possess derived characters
that could be synapomorphic with the unique skeletal structure and
patterns of development of the chelonian skull, carapace or plastron,
which had reached an essentially modern configuration by the Late
Triassic. Numerous molecular biologists have attempted to establish
the closest sister-group of turtles through analyses of a host of
living species, but there is no way for them to preclude turtles from
having evolved from one or another of the Paleozoic or early Mesozoic
clades that have become extinct without leaving any other living
descendants. On the other hand, recent studies of the genetic and
molecular aspects of the development of the carapace and plastron
imply unique patterns of evolutionary change that cannot be recognized
in any of the other amniote lineages, living or dead. This, together
with the retention of a skull without temporal fenestration implies a
very early divergence from a lineage that probably retained an anapsid
skull configuration. This problem may be resolved by more detailed
study of the enigmatic genus Eunotosaurus, from the Late Permian of
South Africa.


Olivier Rieppel (2012)
The Evolution of the Turtle Shell.
Morphology and Evolution of Turtles. Part 2, 51-61
DOI: 10.1007/978-94-007-4309-0_5

This chapter traces the history of the debate on the evolution of the
turtle shell, and carries the analysis of the origin of the turtle
carapace forward from two complementary perspectives, viz.
paleontology and developmental biology. Two alternative approaches to
morphological analysis—the transformationist and the emergentist—are
identified. The transformationist approach seeks to understand
morphological evolution as a consequence of the gradual, step-wise
transformation of the adult phenotype. The emergentist approach allows
for ontogenetic deviation to result in the development of evolutionary
novelties. The discovery of the so far oldest and most primitive
turtle known, from the early Late Triassic of southwestern China,
provides the basis for a synthesis of paleontological and
developmental data in the understanding of the evolutionary origin of
the turtle shell.


Ren Hirayama, Shinji Isaji and Tsuyoshi Hibino (2012)
Kappachelys okurai gen. et sp. nov., a New Stem Soft-Shelled Turtle
from the Early Cretaceous of Japan.
Morphology and Evolution of Turtles. Part 3, 179-185
DOI: 10.1007/978-94-007-4309-0_12

Kappachelys okurai gen. et sp. nov. is named and described based on
two isolated carapacial elements (right seventh costal and left
seventh peripheral) from the Lower Cretaceous (?upper Neocomian)
Akaiwa Formation of west-central Honshu, Japan. Kappachelys is a small
turtle (shell length ~10 cm) that exhibits a unique combination of
three features: coarse and deep vermiculate sculpture on carpace; no
scute sulci; and well-developed peripherals. The form of the sculpture
and lack of scute sulci both suggest affinities with the Trionychidae
(soft-shelled turtles), whereas the plesiomorphic retention of
well-developed peripherals indicates Kappachelys lies outside the
Trionychidae. Given this combination of primitive and derived
features, we interpret Kappechelys as a stem trionychid. In the same
region of Japan, the overlying Lower Cretaceous (Aptian) Kitadani
Formation contains some of the oldest known, unequivocal trionychid
fossils. Based on its slightly older age, similar geographical
distribution, and more primitive shell morphology, Kappachelys could
be ancestral to the trionychids of the Kitadani Formation.


Hiroshi Nagashima, Shigehiro Kuraku, Katsuhisa Uchida, Yoshie
Kawashima-Ohya, Yuichi Narita and Shigeru Kuratani (2012)
Origin of the Turtle Body Plan: The Folding Theory to Illustrate
Turtle-Specific Developmental Repatterning.
Morphology and Evolution of Turtles. Part 2, 37-50
DOI: 10.1007/978-94-007-4309-0_4

The turtle shell is comprised of a dorsal carapace and a ventral
plastron, and is an autapomorphy of this group. The carapace consists
of the vertebral column and ribs as well as a specialized dermis. The
formation of the shell is accompanied by a change in the spatial
relationship of the ribs and the pectoral girdle. Because of this
rearrangement, the turtle shell has been regarded as an example of an
evolutionary novelty. Understanding the changes behind this
developmental repatterning will help us elucidate the evolutionary
history of turtles. The change has been attributed to a deflected
pattern of development of the ribs, which in normal tetrapods grow
ventrally into the lateral body wall. In turtles, they grow laterally
toward the primordium of the carapacial margin, called the carapacial
ridge (CR), while remaining in the axial part of the embryonic body.
Based on a similarity in histological configuration, the CR has been
thought to possess inductive activity for rib growth, as seen in the
apical ectodermal ridge of the amniote limb bud. The CR does not
function as a guidance cue for rib progenitor cells but rather
functions in the marginal growth of the carapacial primordium,
resulting in fanned-out growth of the ribs. This peripheral and
concentric expansion of the axial domain makes the lateral body wall
fold inward, while the ribs cover the pectoral girdle. The turtle ribs
develop along the muscle plate as in other amniotes, and do not take a
different trajectory from that in other amniotes, unlike the scenario
hypothesized previously. This folding enables turtles to change the
apparent spatial relationships between the ribs and the pectoral
girdle without altering their topological alignment and body plan as
amniotes. This developmental sequence of the modern turtles aligns
with a stepwise evolutionary process in the group, which is supported
by the anatomy of a recently discovered fossil species, Odontochelys.


Paul C. Sereno and Sara J. ElShafie (2012)
A New Long-Necked Turtle, Laganemys tenerensis (Pleurodira:
Araripemydidae), from the Elrhaz Formation (Aptian–Albian) of Niger
Morphology and Evolution of Turtles. Part 4, 215-250
DOI: 10.1007/978-94-007-4309-0_14

An articulated skull and postcranial skeleton of a pelomedusoid
turtle, Laganemys tenerensis gen. et sp. nov., is described from the
Lower Cretaceous (Aptian–Albian) Elrhaz Formation in Niger. Laganemys
has a proportionately long skull, which increases in depth anteriorly,
from the occiput to the snout. The thin flat carapace and plastron are
covered with fine sulcus-and-ridge texture. The carapace has a deep
nuchal embayment anteriorly, a small mesoplastron laterally, and three
median fenestrae. The cervical series is nearly as long as the
carapace with specialized joints to enhance lateral flexion between
cervicals 2 and 3 and cervicals 6 and 7. The relatively long tail is
composed of at least 26 vertebrae. Forelimbs and hind limbs have long
and relatively straight unguals. Discovered in a fluvial setting,
Laganemys would have been an adept long-necked aquatic predator in
still waters. A suite of derived features unites Laganemys tenerensis
with Araripemys barretoi, a pelomedusoid from northeastern Brazil of
similar form, habits and geologic age. These genera provide additional
evidence of faunal exchange between South America and Africa in the
mid Cretaceous (ca. 110 Mya) prior to the advent of deep waters in the
central Atlantic Ocean.


Elizabeth T. Smith and Benjamin P. Kear (2012)
Spoochelys ormondea gen. et sp. nov., an Archaic Meiolaniid-Like
Turtle from the Early Cretaceous of Lightning Ridge, Australia.
Morphology and Evolution of Turtles. Part 3, 121-146
DOI: 10.1007/978-94-007-4309-0_9

The Lower Cretaceous (lower to middle Albian) Griman Creek Formation
deposits of Lightning Ridge in central-eastern Australia are famous
for producing opalised fossils. Much of this material is poorly
documented but recent assessments suggest a diverse assemblage of
mainly non-marine vertebrates, invertebrates and plants. This biota is
associated with a Gondwanan high-latitude zone that would have been
subject to cool-temperate conditions. Turtle remains are particularly
common at Lightning Ridge, comprising several distinct lineages
including aquatic chelids and peculiar meiolaniid-like
taxa—meiolaniids were spectacular horned turtles known from the
Australian region and South America. Spoochelys ormondea gen. et sp.
nov. shares some distinctive skeletal traits with this group (e.g.,
cranial scute pattern, incisura columellae auris confluent with the
Eustachian tube) but also retains remarkably plesiomorphic cranial
structures (e.g., an interpterygoid vacuity and short inferior
parietal process) that are otherwise characteristic of Triassic and
Jurassic stem turtles. The placement of meiolaniids and their sister
lineages within Testudines is controversial in recent phylogenies. To
test the relationships of Spoochelys, we used the two most
comprehensive published data sets of fossil Testudinata and rescored a
number of characters. Separate Maximum Parsimony and Bayesian analyses
of both matrices supported recognition of Spoochelys as a primitive
testudinatan but could not confirm its relationships with the
meiolaniid clade. Nevertheless, the persistence of surprisingly
archaic taxa such as Spoochelys into the Early Cretaceous of Australia
implies survival of an ancient Pangean lineage, and brings into
question long-held assumptions of Laurasian affinities for the
meiolaniid-like turtles of Gondwana.