Osteology, Taxonomy, Phylogeny, and Body Shape Changes of Eocene Catostomid and Problematic Catostomid Fishes

• Author / Creator

  Liu, Juan

• Extant catostomid fishes occupy diverse aquatic ecosystems and niches in North America (NA). Less than 3% of catostomid taxonomic richness, or two species, are found outside of NA in Asia. Such adjunct and unbalanced distribution pattern has been established since the late Oligocene, when catostomids disappeared from Asia and became common fishes in NA. Eocene catostomids, representing the oldest fossil records of this family, reached relatively high taxonomic richness in both NA and Asia, and thus are critical to understand evolution of catostomids. This thesis is a study of about 3000 specimens of Eocene catostomids and problematic catostomids. Osteology of 33 extant catostomid species and 11 other otophysans are examined for comparison. Morphological characters are acquired through microscopic examination and CT scans. Cladistic analyses using the parsimony criterion are performed in PAUP 4b10 and TNT 1.5, and explored in MrBayes on XSEDE (3.2.6) using model-based Bayesian inferences through the CIPRES Science Gateway. Analyses of body shape changes and variations of Eocene catostomids are performed using the landmark-based geometric morphometric method. Body shapes of laterally preserved complete fish are captured using surface scanning and digitized with landmarks in TPS utility and TPS dig2, then analysed in MorphoJ 1.06C. First, taxonomy is clarified for Eocene catostomids and problematic catostomids. Of the NA taxa, Amyzon gosiutense, a previously hypothesized junior synonym of A. aggregatum, retains its specific status based on a suite of osteological features. “NewGenus” brevipinne is revised from the nominal Amyzon brevipinne and represents the first known shallow bodied, small sized, fluvial-sediment derived, and loach-like catostomid genus. Of the Asian taxa, Jianghanichthys hubeiensis, which was firstly assigned to Osteochilus of Cyprinidae and later Catostomidae, is suggested to be a stem cypriniform based on osteological comparison and phylogenetic analysis. The first fossil family of Cypriniformes, Jianghanichthyidae, is erected to contain the species. Additional problematic catostomids, which were described as Eocene Osteochilus from south China, are assigned to Jianghanichthyidae and combined into two species: Jianghanichthys sanshuiensis and J. linliensis. New species Amyzon kishenehnicum and Jianghanichthys huachongensis are described from NA and Asia, respectively. Second, the systematic position and intrarelationships of Eocene catostomids were largely unresolved before this study, although they are critical to understand the evolution of the family and Cypriniformes. Three sets of phylogenetic analyses based on different character sets are performed. The first set vouches that Jianghanichthys doesn't belong to any known cypriniform family, but is a basal clade. The second set finds that Amyzon is a basal clade of Catostomidae instead of a member in the Ictiobinae. The third suite of analyses is optimized by maximally utilizing Eocene species and creating an osteological character list. These analyses suggest that most Eocene catostomids (except Plesiomyxocyprinus) were stem taxa of Catostomidae, and “NewGenus” brevipinne represented the most basal clade. Also, known species of Amyzon are not monophyletic, with Asian A. hunanense and NA A. commune being distinctive basal clades. Another Asian genus Plesiomyxocyprinus is sister to all extant catostomids except ictiobines. Third, Eocene catostomids possess similar general appearances and have highly overlapped meristic and morphometric characters, which caused had taxonomic confusion. Quantitative anatomical comparison in this study (geometric morphometrics) finds significant body shape differences between jianghanichthyids and sampled catostomids, A. aggregatum versus A. gosiutense, and A. aggregatum versus A. kishenehnicum. Regression analysis on Procrustes coordinates and centroid sizes shows that allometry does not significantly affect body shapes differences among well-sampled catostomids and jianghanichthyids. Phylogenetically mapped morphospace indicates evolutionary trajectories and trends of body shape changes are congruent to phylogenetic branches of Eocene catostomids and jianghanichthyids. In sum, all unambiguous oldest cypriniforms are included for discussion (Catostomidae, and Jianghanichthyidae of this study plus Cyprinidae). The only area that all oldest cypriniforms are found is south Asia, which suggests that area is the hotspot of origin and cladogenesis of Cypriniformes. Central Asia, including north China, Mongolia, Kazakhstan, and Fareast Russia, where the last remains of catostomid fossils in Asia recorded cyprinids' dispersal route, is a gateway leading to the dispersal events eastward to NA through Beringia and westward to Europe. The mosaic distribution of the Asian taxa across the phylogeny suggests multiple episodes of intercontinental dispersals during the early evolution of catostomids, probably through the freshwater connections of Beringia before the middle Eocene.

• Subjects / Keywords

  • Body shape changes
  • Phylogeny
  • Systematics
  • Eocene
  • Catostomidae
  • Cypriniformes
  • Osteology

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/R3X63BD4W

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.