The Early Evolution of the Tetrapod Humerus

Shubin, Neil H.; Daeschler, Edward B.; Coates, Michael I.

doi:10.1126/science.1094295

Cited by 89 publications

(96 citation statements)

References 13 publications

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“…However, this simple picture should be approached with a degree of caution. ANSP 21350 and Elginerpeton in particular (whether or not the latter taxon is taken to include the disputed humerus GSM 104536; refs 13,38) show character combinations that are substantively different from those of Ventastega and Acanthostega without being obviously autapomorphic, and both probably occupy deep positions in the phylogeny. At a minimum this demonstrates the presence of considerable morphological diversification among the earliest tetrapods.…”

Section: The Postcranial Skeletonmentioning

confidence: 99%

“…It seems that the Famennian tetrapod record has only a poor stratophylogenetic fit, a contention that is further supported by the co-occurrence of the very primitive humerus ANSP 21350 (ref. 38) and much more derived whatcheeriid-like skull elements (J.A.C. personal observation) in the upper Famennian Catskill Formation of Pennsylvania.…”

Section: The Postcranial Skeletonmentioning

confidence: 99%

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Ventastega curonica and the origin of tetrapod morphology

Ahlberg

Clack

Lukševičs

et al. 2008

Nature

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The gap in our understanding of the evolutionary transition from fish to tetrapod is beginning to close thanks to the discovery of new intermediate forms such as Tiktaalik roseae. Here we narrow it further by presenting the skull, exceptionally preserved braincase, shoulder girdle and partial pelvis of Ventastega curonica from the Late Devonian of Latvia, a transitional intermediate form between the 'elpistostegids' Panderichthys and Tiktaalik and the Devonian tetrapods (limbed vertebrates) Acanthostega and Ichthyostega. Ventastega is the most primitive Devonian tetrapod represented by extensive remains, and casts light on a part of the phylogeny otherwise only represented by fragmentary taxa: it illuminates the origin of principal tetrapod structures and the extent of morphological diversity among the transitional forms.The fossil record of Devonian tetrapods, the earliest and most primitive limb-bearing members of the tetrapod stem group, was for many decades restricted to the iconic 'four-legged fish' Ichthyostega from the Famennian (latest Devonian) of Greenland 1-5 and the fragmentary genus Acanthostega from the same strata 2 . During the last 20 years, intense collecting and research has produced complete skeletal material of Acanthostega 6-8 and a series of new taxa, greatly expanding the temporal and geographical range of these animals. Devonian tetrapods are now known from as early as the late Frasnian, the earlier part of the Late Devonian period, and have been recorded from Gondwana and north China as well as Laurussia 9-18 . However, most of these new forms remain very poorly known, typically represented by no more than lower jaw rami or isolated postcranial bones; Acanthostega and Ichthyostega are still the only Devonian tetrapods known from near-complete skeletons. We know less about the fishtetrapod transition than the taxic diversity suggests.Among the more fragmentary forms are five (Metaxygnathus, Densignathus, Elginerpeton, Obruchevichthys and Ventastega) that combine a characteristically tetrapod lower-jaw morphology with the retention of coronoid fangs and other 'fish' characters absent in Acanthostega, Ichthyostega and more crownward limbed members of the tetrapod stem group 19,20 . These genera seem to fall into the morphological gap between Acanthostega and Ichthyostega and the (paraphyletic) elpistostegids, but all except Ventastega are very incomplete. Ventastega was originally described in 1994 from the Pavāri locality in the late Famennian Ketleri Formation of Kurzeme, western Latvia 21 (Supplementary Information 1). Further excavations at this site up to 2001 have yielded an extensive body of material, including previously unknown or incompletely known elements such as a near-complete skull roof plus braincase and associated cheek (Fig. 1), scapulocoracoid, anocleithrum, interclavicle and ilium (Fig. 2). All come from a single horizon, and the occurrence of multiple identical examples of several elements (jaws, cheek plates, maxillae, clavicles, cleithra, nasals) indicates that only ...

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Section: The Postcranial Skeletonmentioning

confidence: 99%

Section: The Postcranial Skeletonmentioning

confidence: 99%

Ventastega curonica and the origin of tetrapod morphology

Ahlberg

Clack

Lukševičs

et al. 2008

Nature

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“…The sequence of character transformations in the pectoral appendicular skeleton that accompanied the fins-to-limbs and water-to-land transitions in tetrapods has been described in detail (e.g. Coates, Jeffery & Ruta, 2002;Shubin, Daeschler & Coates, 2004;Hall, 2008;Boisvert, 2009;Callier, Clack & Ahlberg, 2009;Ahlberg, 2011;Pierce, Clack & Hutchinson, 2012). Changes between tetrapodomorph fish such as Eusthenopteron and Devonian tetrapods such as Acanthostega include the following: in the shoulder girdle, dermal bones spanning the head-trunk boundary were lost and the endoskeletal girdle was enlarged (Coates et al, 2002;, and the orientation of the shoulder joint (glenoid) changed from posterior to posterolateral.…”

Section: Introductionmentioning

confidence: 99%

Reconstructing pectoral appendicular muscle anatomy in fossil fish and tetrapods over the fins‐to‐limbs transition

et al. 2017

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The question of how tetrapod limbs evolved from fins is one of the great puzzles of evolutionary biology. While palaeontologists, developmental biologists, and geneticists have made great strides in explaining the origin and early evolution of limb skeletal structures, that of the muscles remains largely unknown. The main reason is the lack of consensus about appendicular muscle homology between the closest living relatives of early tetrapods: lobe-finned fish and crown tetrapods. In the light of a recent study of these homologies, we re-examined osteological correlates of muscle attachment in the pectoral girdle, humerus, radius, and ulna of early tetrapods and their close relatives. Twenty-nine extinct and six extant sarcopterygians were included in a meta-analysis using information from the literature and from original specimens, when possible. We analysed these osteological correlates using parsimony-based character optimization in order to reconstruct muscle anatomy in ancestral lobe-finned fish, tetrapodomorph fish, stem tetrapods, and crown tetrapods. Our synthesis revealed that many tetrapod shoulder muscles probably were already present in tetrapodomorph fish, while most of the more-distal appendicular muscles either arose later from largely undifferentiated dorsal and ventral muscle masses or did not leave clear correlates of attachment in these taxa. Based on this review and meta-analysis, we postulate a stepwise sequence of specific appendicular muscle acquisitions, splits, and fusions that led from the ancestral sarcopterygian pectoral fin to the ancestral tetrapod forelimb. This sequence largely agrees with previous hypotheses based on palaeontological and comparative work, but it is much more comprehensive in terms of both muscles and taxa. Combined with existing information about the skeletal system, our new synthesis helps to illuminate the genetic, developmental, morphological, functional, and ecological changes that were key components of the fins-to-limbs transition.

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“…Elginerpeton and Obruchevichthys were first, between 385 and 375 MYBP, followed several million years later by a modest radiation that included Ventastega, Ichythostega, Acanthostega, Tulerpeton, Metaxygnathus, and Hynerpeton. Although most of these taxa possessed limbs (although this is not certain for Elginerpeton and Obruchevichthys), all of these taxa have been interpreted as fully aquatic, rather than terrestrial (5)(6)(7). Their respiratory systems are poorly known, but osteology suggests that they were able to derive some amount of O 2 from water instead of being entirely air breathing (8).…”

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confidence: 99%

Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization

Ward

Labandeira

Laurin

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

130

104

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The first terrestrialization of species that evolved from previously aquatic taxa was a seminal event in evolutionary history. For vertebrates, one of the most important terrestrialized groups, this event was interrupted by a time interval known as Romer's Gap, for which, until recently, few fossils were known. Here, we argue that geochronologic range data of terrestrial arthropods show a pattern similar to that of vertebrates. Thus, Romer's Gap is real, occupied an interval from 360 million years before present (MYBP) to 345 MYBP, and occurred when environmental conditions were unfavorable for air-breathing, terrestrial animals. These model results suggest that atmospheric oxygen levels were the major driver of successful terrestrialization, and a low-oxygen interval accounts for Romer's Gap. Results also show that terrestrialization among members of arthropod and vertebrate clades occurred in two distinct phases. The first phase was a 65-million-year ( (1) indicates that arthropods, with species interpreted as fully land-based before 400 million years before present (MYBP) (2), preceded vertebrates onto land by tens of millions of years. The first body fossils identified as stegocephalians (limbed vertebrates) are known from strata Ϸ370 MYBP, such that the appearance of the limb with digits, the loss of the opercular apparatus, and the development of other characters that subsequently allowed a terrestrial lifestyle, presumably occurred during the 25-My interval between 385 and 360 MYBP (3, 4). Most of our understanding about these crucial vertebrate events comes from only a few freshwater deposits from Euramerican localities, with outcrops in Greenland producing the most prolific stegocephalian remains. Elginerpeton and Obruchevichthys were first, between 385 and 375 MYBP, followed several million years later by a modest radiation that included Ventastega, Ichythostega, Acanthostega, Tulerpeton, Metaxygnathus, and Hynerpeton. Although most of these taxa possessed limbs (although this is not certain for Elginerpeton and Obruchevichthys), all of these taxa have been interpreted as fully aquatic, rather than terrestrial (5-7). Their respiratory systems are poorly known, but osteology suggests that they were able to derive some amount of O 2 from water instead of being entirely air breathing (8). These stegocephalians disappeared soon thereafter, followed rapidly by rare appearances of limbed vertebrates. This temporal gap has long been called Romer's Gap, and until recently it was unknown whether this hiatus was due to a combination of unfavorable taphonomic conditions and collection failure or whether it represented an interval of intrinsically low diversity and an abundance of limbed vertebrates. Romer's Gap separates occurrences of the earliest (Late Devonian) aquatic stegocephalians from a much larger adaptive radiation that included the first terrestrial vertebrates that commenced during the Visean stage of the Early Carboniferous. Although new collections have partly filled Romer's Gap (9), including the d...

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The Early Evolution of the Tetrapod Humerus

Cited by 89 publications

References 13 publications

Ventastega curonica and the origin of tetrapod morphology

Ventastega curonica and the origin of tetrapod morphology

Reconstructing pectoral appendicular muscle anatomy in fossil fish and tetrapods over the fins‐to‐limbs transition

Confirmation of Romer's Gap as a low oxygen interval constraining the timing of initial arthropod and vertebrate terrestrialization

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