IX.—The Postcranial Skeleton of<i>Ensthenopteron foordi</i>Whiteaves

Andrews, S. M.; Westoll, T. S.

doi:10.1017/s008045680001471x

Cited by 165 publications

(266 citation statements)

References 64 publications

Supporting

Mentioning

251

Contrasting

Order By: Relevance

“…The humerus transformed from conical, ovoid or pear-shaped to an angular, L-shaped element (e.g. Andrews & Westoll, 1970a;Boisvert, 2009), and the shape of the humeral head changed from circular to strap-like . The radius and ulna transformed from flattened, diverging elements of unequal length to two parallel cylinders articulating distally with multiple carpal bones (Andrews & Westoll, 1970a;Ahlberg, 2011 skeleton lost its dermal fin rays (lepidotrichia) and gained digits.…”

Section: Introductionmentioning

confidence: 99%

“…Andrews & Westoll, 1970a;Boisvert, 2009), and the shape of the humeral head changed from circular to strap-like . The radius and ulna transformed from flattened, diverging elements of unequal length to two parallel cylinders articulating distally with multiple carpal bones (Andrews & Westoll, 1970a;Ahlberg, 2011 skeleton lost its dermal fin rays (lepidotrichia) and gained digits. Functionally, these changes led to the pectoral limb becoming a weight-bearing appendage directed laterally rather than posteriorly (Boisvert, Mark-Kurik & Ahlberg, 2008) with restricted shoulder rotation Pierce et al, 2012;Pierce, Hutchinson, & Clack, 2013), and a flexed elbow (Ahlberg, 2011).…”

Section: Introductionmentioning

confidence: 99%

“…In the early 20th century, A. S. Romer reconstructed appendicular muscle anatomy in early-diverging synapsids (Romer, 1922) and the pectoral limbs of Diadectes and Eogyrinus (Romer, 1924) based on detailed studies of modern taxa. Other notable examples of reconstruction of appendicular muscles include the fossil lungfish Glyptolepis (Ahlberg, 1989), the tetrapodomorph fish Eusthenopteron (Andrews & Westoll, 1970a), the stem tetrapod (i.e. more closely related to extant tetrapods than extant lungfish, but not part of the crown group) Ossinodus (Bishop, 2014), the early temnospondyl amphibian Eryops (Miner, 1925), and various stem amniotes (e.g.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

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

et al. 2017

View full text Add to dashboard Cite

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.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

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

et al. 2017

View full text Add to dashboard Cite

show abstract

“…This hypothesis, which was based partly on the complete absence of plausible digit homologues in Panderichthys (then the closest known relative of tetrapods) 3 , has already been called into question by the discovery of digit-like radials in Tiktaalik 4 and the fact that Hox gene expression patterns closely resembling those associated with digit formation in tetrapods occur in the distal fin skeletons of paddlefish 5 and Australian lungfish 7 . Our new data show that Panderichthys is not an anomaly: like Tiktaalik and other fish members of the Tetrapodomorpha 17,18 it has distal radials that can be interpreted as digit homologues.…”

mentioning

confidence: 67%

“…Given that recent phylogenies consistently place Panderichthys below Tiktaalik in the tetrapod stem group 19,20 , it is surprising to discover that its pectoral fin skeleton is more limb-like than that of its supposedly more derived relative. In Tiktaalik 4 , like in 'osteolepiforms' 17 and rhizodonts 18 (more primitive fish members of the stem group), the ulna and ulnare are of similar size. The axis of the fin comprises two more elements distal to the ulnare, and the distal radials are arranged pinnately around this axis.…”

mentioning

confidence: 99%

The pectoral fin of Panderichthys and the origin of digits

Boisvert

Mark-Kurik

Ahlberg

2008

Nature

121

112

View full text Add to dashboard Cite

One of the identifying characteristics of tetrapods (limbed vertebrates) is the presence of fingers and toes. Whereas the proximal part of the tetrapod limb skeleton can easily be homologized with the paired fin skeletons of sarcopterygian (lobe-finned) fish, there has been much debate about the origin of digits. Early hypotheses 1 interpreted digits as derivatives of fin radials, but during the 1990s the idea gained acceptance that digits are evolutionary novelties without direct equivalents in fish fin skeletons. This was partly based on developmental genetic data 2 , but also substantially on the pectoral fin skeleton of the elpistostegid (transitional fish/ tetrapod) Panderichthys, which appeared to lack distal digit-like radials 3 . Here we present a CT scan study of an undisturbed pectoral fin of Panderichthys demonstrating that the plate-like 'ulnare' of previous reconstructions is an artefact and that distal radials are in fact present. This distal portion is more tetrapod-like than that found in Tiktaalik 4 and, in combination with new data about fin development in basal actinopterygians 5 , sharks 6 and lungfish 7 , makes a strong case for fingers not being a novelty of tetrapods but derived from pre-existing distal radials present in all sarcopterygian fish.A near-complete specimen of Panderichthys from the late Middle Devonian period (385 million years ago; see Supplementary Information) of Lode, Latvia (Institute of Geology at Tallinn University of Technology specimen number GIT434-1) forms the basis of this study. Although the dorsal part of the skull and left side of the body have suffered substantial damage from a mechanical excavator, the specimen was originally well preserved. Notably, its body axis is straight (determined from the alignment of dorsal midline scales and the symmetry plane of the skull) and it appears less dorsoventrally compressed than others from the same locality. This is shown, for example, by the narrow skull outline and near-vertical cheek-plate fragments, distinctly different from the flattened and splayed skulls that have been published 8,9 . The specimen also contains the only known pelvis and pelvic fin skeleton of Panderichthys 10 .The right pectoral fin and most of the shoulder girdle are preserved in articulation, with the fin concealed under the body. This region of the specimen was CT scanned at the East-Tallinn Central Hospital (see Methods Summary and Supplementary Methods). The scanned region comprises the entire fin endoskeleton and an estimated 40% of the lepidotrichial fin web, as well as most of the shoulder girdle. The presence of X-ray-reflective crystal growths in the shoulder region unfortunately prevented complete modelling of the scapulocoracoid. The entire fin is covered by scales and lepidotrichia, which cannot be modelled individually but are easily separated from the darker endoskeleton. The leading or preaxial margin of the fin is dipping ventrolaterally into the substrate (Fig. 1a-c). In contrast to early tetrapods, in which the limb projects at...

show abstract

The Amphibian World

Schoch¹

2014

Amphibian Evolution

View full text Add to dashboard Cite

IX.—The Postcranial Skeleton ofEnsthenopteron foordiWhiteaves

Cited by 165 publications

References 64 publications

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

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

The pectoral fin of Panderichthys and the origin of digits

The Amphibian World

Contact Info

Product

Resources

About