Hand and Foot Musculature of Anura: Structure, Homology, Terminology, and Synapomorphies for Major Clades
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HAND AND FOOT MUSCULATURE OF ANURA: STRUCTURE, HOMOLOGY, TERMINOLOGY, AND SYNAPOMORPHIES FOR MAJOR CLADES BORIS L. BLOTTO, MARTÍN O. PEREYRA, TARAN GRANT, AND JULIÁN FAIVOVICH BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY HAND AND FOOT MUSCULATURE OF ANURA: STRUCTURE, HOMOLOGY, TERMINOLOGY, AND SYNAPOMORPHIES FOR MAJOR CLADES BORIS L. BLOTTO Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil; División Herpetología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”–CONICET, Buenos Aires, Argentina MARTÍN O. PEREYRA División Herpetología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”–CONICET, Buenos Aires, Argentina; Laboratorio de Genética Evolutiva “Claudio J. Bidau,” Instituto de Biología Subtropical–CONICET, Facultad de Ciencias Exactas Químicas y Naturales, Universidad Nacional de Misiones, Posadas, Misiones, Argentina TARAN GRANT Departamento de Zoologia, Instituto de Biociências, Universidade de São Paulo, São Paulo, Brazil; Coleção de Anfíbios, Museu de Zoologia, Universidade de São Paulo, São Paulo, Brazil; Research Associate, Herpetology, Division of Vertebrate Zoology, American Museum of Natural History JULIÁN FAIVOVICH División Herpetología, Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”–CONICET, Buenos Aires, Argentina; Departamento de Biodiversidad y Biología Experimental, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires, Buenos Aires, Argentina; Research Associate, Herpetology, Division of Vertebrate Zoology, American Museum of Natural History BULLETIN OF THE AMERICAN MUSEUM OF NATURAL HISTORY Number 443, 155 pp., 14 plates, 1 table Issued November 6, 2020 Copyright © American Museum of Natural History 2020 ISSN 0003-0090 CONTENTS Abstract.............................................................................3 Introduction.........................................................................3 Materials and Methods................................................................5 Results.............................................................................10 Description of the Hand and Foot Musculature of Triprion petasatus ...................10 Character Evolution...............................................................24 Discussion .........................................................................30 Systematic Implications of the Inferred Synapomorphies...............................30 Homology and Terminology: A Reappraisal..........................................38 Origin of Novelties in the Anuran Hand and Foot Musculature.........................54 Conclusions ........................................................................56 Acknowledgments...................................................................57 References..........................................................................57 Appendix 1. Specimens examined .....................................................64 Appendix 2. Comments on phalanx terminology ........................................68 Appendix 3. Anuran hand and foot musculature: synonym list ............................70 Appendix 4. Data matrix ........................................................... 112 Appendix 5. Ancestral character state reconstructions.................................. 116 Appendix 6. Abbreviations. ......................................................... 136 Plates ............................................................................ 137 2 ABSTRACT Although studies of anuran hand and foot musculature began in the first half of the 19th century, all studies to date have been taxonomically or anatomically restricted in scope, and none has con- sidered the diversity of autopodial myology in Anura as a whole. As a model for future comparisons, we thoroughly describe the hand and foot musculature of an arboreal species (the hylid Triprion petasatus), define the layers in which these muscles are arranged, and attribute presumed functions. On the basis of our myological analysis of 155 species representing 46 of the 54 currently recognized families and main clades of anurans, we describe 20 characters related to hand and foot muscles. Optimization of these characters on the most recent and inclusive phylogenetic hypothesis of Anura results in synapomorphies for several major clades (Bombinatoridae, Alytidae, Xenoanura + Acos- manura, Xenoanura, Pipidae, Acosmanura, Anomocoela, Scaphiopodidae, Pelodytidae + Pelobatidae + Megophryidae, Megophryidae, Neobatrachia, Heleophrynidae, Sooglossidae, Laurentobatrachia, Calyptocephalellidae, Myobatrachoidea, and Nobleobatrachia), including new, nonhomoplastic syn- apomorphies for clades previously supported only by molecular evidence and a few conflicting phenotypic characters (e.g., Acosmanura, Anomocoela, Neobatrachia). Additionally, we (1) address controversies regarding the homology of anuran and caudate muscles in the context of putative synapomorphies for Ascaphidae + Leiopelmatidae and its sister clade Lalagobatrachia; (2) evaluate a recently proposed terminology for anuran hand and foot musculature; (3) discuss the identities of several hand and foot muscles with problematic homologies; (4) establish a unified terminology for anuran hand and foot muscles, including a list of synonyms for all names employed in the literature; and (5) propose hypotheses for the origin of several myological novelties (neomorphs). INTRODUCTION lineages, Burton (2004) focused on the foot mus- culature of “Hylidae” (including Hemiphractidae). Over the last 15 years, several studies have con- Both the larval and foot musculature studies pro- tributed significantly to the knowledge of phylo- posed several synapomorphies for a number of genetic relationships of major groups of Anura. groups, and their data sets were included in total Most of these studies were based exclusively on evidence analyses by Frost et al. (2006) and DNA sequences (e.g., Darst and Cannatella, 2004; Faivovich et al. (2005), respectively. However, the Roelants et al., 2007; Heinicke et al., 2009; Wiens dearth of comparable data sets prevents these et al., 2010; San Mauro, 2010; Pyron and Wiens, character systems from being used to test hypoth- 2011; Fouquet et al., 2013; Barej et al., 2014; Padial eses across Anura. et al., 2014; Pyron, 2014; Brown et al., 2015; Phenotypic synapomorphies are unknown for Frazão et al., 2015; Chan and Brown, 2017; Feng several major clades of anurans due to the lack of et al., 2017; Mahony et al., 2017; Chan et al., 2018; comprehensive studies for most character sys- Jetz and Pyron, 2018; Streicher et al., 2018; Tu et tems. This scenario underscores the need to al., 2018), while a few of them also included phe- explore multiple phenotypic sources of evidence notypic datasets (Faivovich et al., 2005; Scott, to bear on phylogenetic hypotheses. The detailed 2005; Wiens et al., 2005; Frost et al., 2006; Grant study of phenotypic character systems provides et al., 2006, 2017) and even fewer focused exclu- homology hypotheses that are instrumental for sively on phenotypic characters—Haas (2003), the study of the morphological evolution of a Púgener et al. (2003), and Burton (2004) the clade (e.g., O’Leary et al., 2013). Furthermore, it major examples. Whereas Haas (2003) and allows the establishment of a bridge between pat- Púgener et al. (2003) employed primarily larval tern and process, enabling the exploration of characters scored for exemplars of major anuran evolutionary mechanisms and formulation of 3 4 BULLETIN AMERICAN MUSEUM OF NATURAL HISTORY NO. 443 testable functional hypotheses (e.g., Wake et al., musculature of “Hylidae” (including Hemi- 2011). Ultimately, the inclusion of phenotypic phractidae), which Faivovich et al. (2005) data in total evidence phylogenetic analyses has combined with DNA sequences in a total evi- been shown to have a disproportionately large dence analysis. Manzano et al. (2008) studied effect, influencing tree topology and clade sup- characters related to specializations for grasp- port estimations, and, therefore, taxonomic deci- ing in the forelimb of two hylids. Salgar et al. sions (e.g., Nylander et al., 2004; de Sá et al., (2009) reported on the foot musculature of a 2014; Mirande, 2017; Sánchez-Pacheco et al., species of Pristimantis (Craugastoridae), 2018; Cabra-García and Hormiga, 2019). whereas Hoyos et al. (2014) defined characters Hand and foot muscles are an underexplored of foot musculature in a quantitative phyloge- source of phenotypic data. The seminal works of netic analysis of the Pristimantis unistrigatus Dugés (1834), Ecker (1864), Perrin (1892), species group, and Hoyos and Salgar (2016) Gaupp (1896), and Ribbing (1907, 1909, 1911) focused on variation within Dendropsophus described in detail the musculature of a few luddeckei (as D. labialis; Hylidae). Diogo and anuran species, but few subsequent additional Ziermann (2014) studied the development of studies dealt with this character system until the the fore‐ and hind-limb muscles using Eleu- end of the 1990s, and those that did mostly therodactylus coqui (Eleutherodactylidae) as a focused on single species (e.g., Davies and Bur- model. Blotto et al. (2017) described the foot ton, 1982; Burton, 1983) or a limited number of musculature of Odontophrynidae, proposed characters (e.g., Liem, 1970; Burton, 1986). The synapomorphies, and discussed putative adap- sole exception in that period is Dunlap (1960), tations for burrowing. Finally, some studies who studied a diverse