Contrasting Developmental Trajectories in the Earliest Known Tetrapod Forelimbs

  title={Contrasting Developmental Trajectories in the Earliest Known Tetrapod Forelimbs},
  author={Viviane Callier and Jennifer Alice Clack and Per Erik Ahlberg},
  pages={364 - 367}
Ichthyostega and Acanthostega are the earliest tetrapods known from multiple near-complete skeletons, with Acanthostega generally considered the more primitive. New material indicates differing ontogenetic trajectories for their forelimbs: In Ichthyostega, the pattern of muscle attachment processes on small humeri (upper arm bones) resembles that in “fish” members of the tetrapod stem group such as Tiktaalik, whereas large humeri approach (but fail to attain) the tetrapod crown-group condition… 

Developmental plasticity and the origin of tetrapods

The remarkable correspondence between the environmentally induced phenotypes of terrestrialized Polypterus and the ancient anatomical changes in stem tetrapods is shown, raising the possibility that environmentally induced developmental plasticity facilitated the origin of the terrestrial traits that led to tetrapod.

Historical perspectives on the evolution of tetrapodomorph movement.

A phylogenetic review of modern analogs, from chondrichthyans to mammals, highlights the broad spectrum of vertebrate clades and locomotor behaviors, and proposes that various locomotion behaviors of modern quadrupeds can be ruled out for Ichthyostega, but that forelimb "crutching" motions, as seen in living mudskippers, may have been possible.

Early Tetrapods: Experimenting with Form and Function

This chapter describes the ear regions of tetrapods from the Paleozoic. In the past couple of decades, understanding of their morphology has been increased by discoveries of fossils from the Late

A new elpistostegalian from the Late Devonian of the Canadian Arctic

A new elpistostegalian from the Late Devonian period of the Canadian Arctic that shows surprising disparity in the group, and shows specializations for swimming that are unlike those known from other sarcopterygians.

Life history of the stem tetrapod Acanthostega revealed by synchrotron microtomography

The first, to the authors' knowledge, life history data for a Devonian tetrapod, from the Acanthostega mass-death deposit of Stensiö Bjerg, East Greenland is presented, showing that even the largest individuals from this deposit are juveniles.

Non-marine palaeoenvironment associated to the earliest tetrapod tracks

A new palaeoenvironmental interpretation of the track-bearing interval from Zachełmie is presented, showing that it represents a succession of ephemeral lakes with a restricted and non-marine biota, rather than a marginal marine environment as originally thought.

A partial lower jaw of a tetrapod from “Romer's Gap”

ABSTRACT The first half of the Mississippian or Early Carboniferous (Tournaisian to mid- Viséan), an interval of about 20 million years, has become known as “Romer's Gap” because of its poor tetrapod

Tetrapod trackways from the early Middle Devonian period of Poland

Well-preserved and securely dated tetrapod tracks from Polish marine tidal flat sediments of early Middle Devonian (Eifelian stage) age are presented, forcing a radical reassessment of the timing, ecology and environmental setting of the fish–tetrapod transition, as well as the completeness of the body fossil record.

Morphology of the earliest reconstructable tetrapod Parmastega aelidae

Three-dimensionally preserved fossils of Parmastega aelidae, a newly described tetrapod from the earliest Famennian (Late Devonian) of Russia, provide detailed insights into the morphology and palaeobiology of the earliest tetrapods.

Earliest Carboniferous tetrapod and arthropod faunas from Scotland populate Romer's Gap

It is concluded that the gap in the fossil record has been an artifact of collection failure and a series of discoveries of Tournaisian-age localities in Scotland that have yielded a wealth of new tetrapod and arthropod fossils.



The axial skeleton of the Devonian tetrapod Ichthyostega

A new reconstruction of Ichthyostega is shown based on extensive re-examination of original material and augmented by recently collected specimens and reveals hitherto unrecognized regionalization in the vertebral column.

The Early Evolution of the Tetrapod Humerus

A comparative analysis of this fossil and other relevant humeri from the Devonian shows that the role of the limb in propping the body arose first in fish fins, not tetrapod limbs.

Ventastega curonica and the origin of tetrapod morphology

The skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica are presented, a transitional intermediate form between the ‘elpistostegids’ Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega.

The postcranial skeleton of the Devonian tetrapod Tulerpeton curtum Lebedev

A cladistic analysis indicates that Tulerpeton is a reptiliomorph stem-group amniote and the earliest known crown-group tetrapod: Acanthostega and Ichthyostega are successively more derived plesion stem- group tetrapods and do not consititute a monophyletic ichthyostegalian radiation.

IX.—The Postcranial Skeleton of Ensthenopteron foordi Whiteaves

A functional analysis of the skeleton of Ensthenopteron is attempted, suggesting that it resembled the pike in its mode of life and that it may have been capable of short journeys “walking” overland.

The postcranial skeletal anatomy of the carboniferous tetrapod Greererpeton burkemorani Romer, 1969

A cladistic analysis indicates that Greererpeton burkemorani shares a more recent common ancestor with the anthracosaur Proterogyrinus scheelei than it does with either Crassigyrinus scoticus or Ichthyostega sp.

Pederpes finneyae, an articulated tetrapod from the tournaisian of Western Scotland

The postcranial skeleton of Pederpes shows several unique features, including the structure of the leading edges of the cleithrum and clavicle, the form of the rib flanges and a possible supernumerary digit on the manus.

The Carboniferous Amphibian Proterogyrinus scheelei Romer, and the Early Evolution of Tetrapods

Proterogyrinus scheelei Romer, from the Upper Mississippian of Greer, West Virginia, is one of the earliest known members of the amphibian infraorder Embolomeri, and has no undisputed synapomorphies with reptiles either, making it impossible to support close relationship between the two groups.

The pectoral fin of Tiktaalik roseae and the origin of the tetrapod limb

The pectoral appendage of a member of the sister group of tetrapods, Tiktaalik roseae, is described, which is morphologically and functionally transitional between a fin and a limb.

Taxonomic revision of the Late Devonian tetrapod Ichthyostega from East Greenland

  • H. Blom
  • Environmental Science, Geography
  • 2005
Abstract:  Two morphologically distinct assemblages of the Late Devonian tetrapod Ichthyostega from East Greenland are described on the basis of a large collection of skulls and postcranial elements.