Limb-Bone Development of Seymouriamorphs: Implications for the Evolution of Growth Strategy in Stem Amniotes

Estefa, Jordi; Klembara, Jozef; Tafforeau, Paul; Sanchez, Sophie

doi:10.3389/feart.2020.00097

Cited by 12 publications

(16 citation statements)

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“…There is no endosteal bone on the surface of the medullary cavity. Very few remnants of calcified cartilage were found in the metaphysis of the adult humerus, that is in much lower frequency than in the juvenile specimen ( Estefa et al, 2020 ). The spongiosa contains a few longitudinal interconnected marrow processes (100 µm in diameter, Figure 8Bb-c and 10C , Table 2 ).…”

Section: Resultsmentioning

confidence: 83%

“…The spongiosa occupies the entire bone area ( Figure 7A ). The metaphyseal trabeculae are about four times thinner (25 µm on average) than the diaphyseal trabeculae (94 µm on average, Table 2 and Estefa et al, 2020 ). A longitudinal section reveals that the trabecular mesh becomes denser towards the distal and proximal ends of the bone ( Figure 7Aa1-2 ).…”

Section: Resultsmentioning

confidence: 97%

“…The diaphyseal and metaphyseal microarchitectures of the stem tetrapods Eusthenopteron and Hyneria were described by Sanchez et al, 2014 and Kamska et al, 2018 , respectively. The diaphysis of Discosauriscus ( Sanchez et al, 2008 ), Apateon ( Sanchez et al, 2010a ; Sanchez et al, 2010b ), Metoposaurus ( Konietzko-Meier and Sander, 2013 ) and Seymouria ( Estefa et al, 2020 ) were thoroughly described, but the metaphyseal organisation of their humeri was only succinctly mentioned in the cited articles. Here, we provide a detailed description of them ( Table 1 ) in 3D when possible.…”

Section: Resultsmentioning

confidence: 99%

“…In the metaphysis, the trabecular mesh is mostly arranged longitudinally (obviously appearing purple and progressively shifting to green as the deltopectoral crest tilts to 90 degrees, Figure 7Aa2 ) although a few anastomoses (highlighted in green in most of the metaphysis apart from the tilted region of the deltopectoral crest, Figure 7Aa2 ) run radially. A few remnants of calcified cartilage ( Francillon-Vieillot et al, 1990 ) are very rarely visible ( Estefa et al, 2020 ). Marrow processes form an intricate network, while anastomosing to each other, and connecting to cavities of irregular shapes and sizes ( Figure 7Ba,c and 10B ).…”

Section: Resultsmentioning

confidence: 99%

“…The cortex is almost inexistent in the metaphysis ( Figure 8Bb ). The thickness of the trabeculae averages 30 µm ( Table 2 , Estefa et al, 2020 ), which is equivalent to the thickness of the trabeculae in the juvenile metaphysis (MNG 7747). There is no endosteal bone on the surface of the medullary cavity.…”

Section: Resultsmentioning

confidence: 99%

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New light shed on the early evolution of limb-bone growth plate and bone marrow

Estefa

Tafforeau

Clement

et al. 2021

eLife

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The production of blood cells (haematopoiesis) occurs in the limb bones of most tetrapods but is absent in the fin bones of ray-finned fish. When did long bones start producing blood cells? Recent hypotheses suggested that haematopoiesis migrated into long bones prior to the water-to-land transition and protected newly-produced blood cells from harsher environmental conditions. However, little fossil evidence to support these hypotheses has been provided so far. Observations of the humeral microarchitecture of stem-tetrapods, batrachians, and amniotes were performed using classical sectioning and three-dimensional synchrotron virtual histology. They show that Permian tetrapods seem to be among the first to exhibit a centralised marrow organisation, which allows haematopoiesis as in extant amniotes. Not only does our study demonstrate that long-bone haematopoiesis was probably not an exaptation to the water-to-land transition but it sheds light on the early evolution of limb-bone development and the sequence of bone-marrow functional acquisitions.

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Section: Resultsmentioning

confidence: 83%

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

See 3 more Smart Citations

New light shed on the early evolution of limb-bone growth plate and bone marrow

Estefa

Tafforeau

Clement

et al. 2021

eLife

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Evidence of large terrestrial seymouriamorphs in the lowermost Permian of the Czech Republic

Calábková

Březina

Madzia

2022

Papers in Palaeontology

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Lower Permian strata of the Boskovice Basin in the Czech Republic have yielded hundreds of largely complete seymouriamorph individuals, some of which are exceptionally preserved and have noticeable soft tissues, such as external gills and eye structures. The vast majority of these finds are referable to Discosauriscus austriacus, and almost exclusively represent larvae and juveniles tied to aquatic environments. Only one of the specimens discovered to date has been interpreted as an early adult, although late juvenile and early sub‐adult stages have been proposed for it as well. Regardless, no other seymouriamorph adults have been reported from the Boskovice Basin so far. Here we present the first comprehensive assessment of seymouriamorph tracks and a trackway from the Asselian (lowermost Permian) of the Boskovice Basin. The morphology of the tracks is congruent with that of the ichnotaxon Amphisauropus and indicates an attribution to Discosauriscidae or that they belong to as yet unrecognized large seymouriamorphs. All tracks were made by individuals much larger than the largest discosauriscid known from bodily preserved material and are interpreted as those of adults tied to terrestrial environments, thus apparently documenting a habitat shift that occurred relatively late in the ontogenetic development of these seymouriamorphs. Furthermore, the largest track is preserved in extraordinary detail and includes soft part impressions such as digital, palmar and plantar flexion creases, making the specimen one of the best preserved seymouriamorph tracks described to date. Finally, one of the tracks originates from the lowermost Asselian and is therefore among the oldest known records of seymouriamorphs worldwide.

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The postcranial anatomy ofWhatcheeria deltaeand its implications for the family Whatcheeriidae

Otoo

Bolt

Lombard

et al. 2021

Zoological Journal of the Linnean Society

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Here we describe the postcranial skeleton and present the first full-body reconstruction of the early tetrapod Whatcheeria deltae from the Viséan of Iowa. The skeletal proportions, including an elongate neck and large limbs, are unlike those of other Devonian and Mississippian tetrapods. The robust limbs of Whatcheeria appear adapted for a walking gait, but the lateral lines of the cranium are fundamentally unsuited for sustained subaerial exposure. Thus, although Whatcheeria bears a general resemblance to certain terrestrially adapted Permian and Triassic members of crown tetrapod lineages, its unusual form signals a broader range of early amphibious morphologies and habits than previously considered. From the exceptionally rich collection it is evident that most Whatcheeria specimens represent immature individuals. Rare specimens suggest an adult body size of at least 2 m, over twice that of the holotype. Further comparison suggests that the Pederpes holotype might also be a juvenile and reveals a combination of hindlimb characters unique to Whatcheeria and Pederpes. These new data contribute to a revised diagnosis of the family Whatcheeriidae and a re-evaluation of fragmentary Devonian–Carboniferous fossils reported as ‘whatcheeriid’ but sharing no synapomorphies with the more precisely defined clade.

show abstract

Limb-Bone Development of Seymouriamorphs: Implications for the Evolution of Growth Strategy in Stem Amniotes

Cited by 12 publications

References 80 publications

New light shed on the early evolution of limb-bone growth plate and bone marrow

New light shed on the early evolution of limb-bone growth plate and bone marrow

Evidence of large terrestrial seymouriamorphs in the lowermost Permian of the Czech Republic

The postcranial anatomy ofWhatcheeria deltaeand its implications for the family Whatcheeriidae

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