New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition.
From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a n...
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| Format: | Article |
| Language: | English |
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Public Library of Science (PLoS)
2014-09-01
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| Series: | PLoS Biology |
| Online Access: | http://europepmc.org/articles/PMC4181957?pdf=render |
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| author | João Francisco Botelho Luis Ossa-Fuentes Sergio Soto-Acuña Daniel Smith-Paredes Daniel Nuñez-León Miguel Salinas-Saavedra Macarena Ruiz-Flores Alexander O Vargas |
| author_facet | João Francisco Botelho Luis Ossa-Fuentes Sergio Soto-Acuña Daniel Smith-Paredes Daniel Nuñez-León Miguel Salinas-Saavedra Macarena Ruiz-Flores Alexander O Vargas |
| author_sort | João Francisco Botelho |
| collection | DOAJ |
| description | From early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal-anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal-anterior ossification does not support the dinosaur-bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal-posterior ossification develops from a cartilage referred to as "element x," but its position corresponds to distal carpal 3. The proximal-posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal-posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications. |
| first_indexed | 2024-12-19T15:42:29Z |
| format | Article |
| id | doaj.art-9a867d0522d544ceaf0b18c59b3c1182 |
| institution | Directory Open Access Journal |
| issn | 1544-9173 1545-7885 |
| language | English |
| last_indexed | 2024-12-19T15:42:29Z |
| publishDate | 2014-09-01 |
| publisher | Public Library of Science (PLoS) |
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| series | PLoS Biology |
| spelling | doaj.art-9a867d0522d544ceaf0b18c59b3c11822022-12-21T20:15:26ZengPublic Library of Science (PLoS)PLoS Biology1544-91731545-78852014-09-01129e100195710.1371/journal.pbio.1001957New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition.João Francisco BotelhoLuis Ossa-FuentesSergio Soto-AcuñaDaniel Smith-ParedesDaniel Nuñez-LeónMiguel Salinas-SaavedraMacarena Ruiz-FloresAlexander O VargasFrom early dinosaurs with as many as nine wrist bones, modern birds evolved to develop only four ossifications. Their identity is uncertain, with different labels used in palaeontology and developmental biology. We examined embryos of several species and studied chicken embryos in detail through a new technique allowing whole-mount immunofluorescence of the embryonic cartilaginous skeleton. Beyond previous controversy, we establish that the proximal-anterior ossification develops from a composite radiale+intermedium cartilage, consistent with fusion of radiale and intermedium observed in some theropod dinosaurs. Despite previous claims that the development of the distal-anterior ossification does not support the dinosaur-bird link, we found its embryonic precursor shows two distinct regions of both collagen type II and collagen type IX expression, resembling the composite semilunate bone of bird-like dinosaurs (distal carpal 1+distal carpal 2). The distal-posterior ossification develops from a cartilage referred to as "element x," but its position corresponds to distal carpal 3. The proximal-posterior ossification is perhaps most controversial: It is labelled as the ulnare in palaeontology, but we confirm the embryonic ulnare is lost during development. Re-examination of the fossil evidence reveals the ulnare was actually absent in bird-like dinosaurs. We confirm the proximal-posterior bone is a pisiform in terms of embryonic position and its development as a sesamoid associated to a tendon. However, the pisiform is absent in bird-like dinosaurs, which are known from several articulated specimens. The combined data provide compelling evidence of a remarkable evolutionary reversal: A large, ossified pisiform re-evolved in the lineage leading to birds, after a period in which it was either absent, nonossified, or very small, consistently escaping fossil preservation. The bird wrist provides a modern example of how developmental and paleontological data illuminate each other. Based on all available data, we introduce a new nomenclature for bird wrist ossifications.http://europepmc.org/articles/PMC4181957?pdf=render |
| spellingShingle | João Francisco Botelho Luis Ossa-Fuentes Sergio Soto-Acuña Daniel Smith-Paredes Daniel Nuñez-León Miguel Salinas-Saavedra Macarena Ruiz-Flores Alexander O Vargas New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. PLoS Biology |
| title | New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. |
| title_full | New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. |
| title_fullStr | New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. |
| title_full_unstemmed | New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. |
| title_short | New developmental evidence clarifies the evolution of wrist bones in the dinosaur-bird transition. |
| title_sort | new developmental evidence clarifies the evolution of wrist bones in the dinosaur bird transition |
| url | http://europepmc.org/articles/PMC4181957?pdf=render |
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