Stem sarcopterygians have primitive polybasal fin articulation

Min Zhu, Xiaobo Yu

Research output: Contribution to journalArticlepeer-review

37 Scopus citations

Abstract

Among osteichthyans, basal actinopterygian fishes (e.g. paddlefish and bowfins) have paired fins with three endoskeletal components (pro-, meso- and metapterygia) articulating with polybasal shoulder girdles, while sarcopterygian fishes (lungfish, coelacanths and relatives) have paired fins with one endoskeletal component (metapterygium) articulating with monobasal shoulder girdles. In the fin-limb transition, the origin of the sarcopterygian paired fins triggered new possibilities of fin articulation and movement, and established the proximal segments (stylopod and zeugopod) of the presumptive tetrapod limb. Several authors have stated that the monobasal paired fins in sarcopterygians evolved from a primitive polybasal condition. However, the fossil record has been silent on whether and when the inferred transition took place. Here we describe three-dimensionally preserved shoulder girdles of two stem sarcopterygians (Psarolepis and Achoania) from the Lower Devonian of Yunnan, which demonstrate that stem sarcopterygians have polybasal pectoral fin articulation as in basal actinopterygians. This finding provides a phylogenetic and temporal constraint for studying the origin of the stylopod, which must have originated within the stem sarcopterygian lineage through the loss of the propterygium and mesopterygium.

Original languageEnglish
Pages (from-to)372-375
Number of pages4
JournalBiology Letters
Volume5
Issue number3
DOIs
StatePublished - 23 Jun 2009

Keywords

  • Fin-limb transition
  • Polybasal fin articulation
  • Sarcopterygians
  • Shoulder girdle
  • Stylopod

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