Evolutionary homology in the fin-to-limb transition: evaluating the morphology of foramina in a Late Devonian humerus from the Catskill Formation, Clinton County, Pennsylvania

Wynd, Brenen M.; Daeschler, Edward B.; Stocker, Michelle R.

doi:10.1080/02724634.2019.1718682

Cited by 1 publication

(1 citation statement)

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“…In particular, the evolutionary origin of the digit and wrist (i.e., the autopod) has been gradually unraveled through paleontological studies of Devonian fossils (Shubin et al, 2006;Cloutier et al, 2020) and through evolutionary developmental studies focused mainly on the 5'Hox genes expressed in fin and limb buds (Shubin and Alberch, 1986;Davis et al, 2007;Johanson et al, 2007;Nakamura et al, 2016;Tanaka, 2016;Woltering et al, 2020). These studies have dispelled any uncertainty about the homologies of proximal (i.e., the stylopod and zeugopod) skeletal elements in fins and limbs, and the morphological transitions from one to the other have been traced in relation to the evolution of tetrapod limb movement (Shubin et al, 2004(Shubin et al, , 2006Pierce et al, 2012;Miyake et al, 2016;Molnar et al, 2017;Ahlberg, 2019;Wynd et al, 2019).…”

Section: Introductionmentioning

confidence: 99%

Development of the Pectoral Lobed Fin in the Australian Lungfish Neoceratodus forsteri

et al. 2021

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The evolutionary transition from paired fins to limbs involved the establishment of a set of limb muscles as an evolutionary novelty. In parallel, there was a change in the topography of the spinal nerves innervating appendicular muscles, so that distinct plexuses were formed at the bases of limbs. However, the key developmental changes that brought about this evolutionary novelty have remained elusive due to a lack of data on the development of lobed fins in sarcopterygian fishes. Here, we observed the development of the pectoral fin in the Australian lungfish Neoceratodus forsteri (Sarcopterygii) through synchrotron radiation X-ray microtomography. Neoceratodus forsteri is a key taxon for understanding the fin-to-limb transition due to its close phylogenetic relationships to tetrapods and well-developed lobed fins. At the onset of the fin bud in N. forsteri, there is no mesenchyme at the junction between the axial body wall and the fin bud, which corresponds to the embryonic position of the brachial plexus formed in the mesenchyme in tetrapods. Later, concurrent with the cartilage formation in the fin skeleton, the fin adductor and abductor muscles become differentiated within the surface ectoderm of the fin bud. Subsequently, the girdle muscle, which is homologous to the tetrapod serratus muscle, newly develops at the junction between the axial body wall and the fin. Our study suggests that the acquisition of embryonic mesenchyme at the junction between the axial body wall and the appendicular bud opened the door to the formation of the brachial plexus and the specialization of individual muscles in the lineage that gave rise to tetrapods.

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