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Anatomical Comparison of the Cephalic Musculature of Some Members of the Superfamily Myliobatoidea (Chondrichthyes): Implications for Evolutionary Understanding.

JasminFlorian
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  1. Anatomical Comparison of the Cephalic Musculature of Some Members of the Superfamily Myliobatoidea (Chondrichthyes): Implications for Evolutionary Understanding Gonzalez-Isais M. 2003. Anatomical Comparison of the Cephalic Musculature of Some Members of the Superfamily Myliobatoidea (Chondrichthyes): Implications for Evolutionary Understanding. The Anatomical Record Part A 271A: 259-272.

  2. Background Information: © Tracy Clark http://www.divebums.com/FishID/Pages/butterfly_ray.html Myliobatoidea

  3. Myliobatoidea Species Studied: Gymnura marmorata (GMA) California Butterfly Ray http://www.fishbase.org.ph/Summary/SpeciesSummary.cfm?id=2578 Gymnura micrura (GMI) Smooth Butterfly Ray http://filaman.uni-kiel.de/Summary/SpeciesSummary.cfm?ID=257

  4. Aetobatus narinari (AN) Spotted Eagle Ray http://www.fishbase.org Mobula munkiana (MM) Munk’s Devil Ray http://www.fishbase.org Mobula thurstoni (MT) Bentfin Devil Ray http://www.fishbase.org

  5. Myliobatis californica (MC) Bat Eagle Ray http://www.fishbase.org Myliobatis longirostris (ML) Snouted Eagle Ray http://www.fishbase.org Rhinoptera steindachneri (RS) Pacific Cownose Ray Http://www.fishbase.org

  6. Muscles of the Dorsal Cephalic Region • Precranial muscle (PM) • Ethmoideo-parethmoidalis muscle (EPE) • *Dorsal longitudinal bundles (DLB) • Levator hyomandibulae muscle (LHM) • Levator spiracularis muscle (LS) • Superficial dorsal constrictor muscles 1-5 (DC1-DC5) • Constrictor hyoideus dorsalis (CHD) • *Cucullaris muscle (CC)

  7. Depressor rostri muscle (DR) *Superficial transverse (ST) muscle and superficial ventral constrictors (VC1-VC5) Coracoarcualis muscle (CA) *Coracomandibular muscle (CM) Suborbitalis muscle (SB) Adductor mandibulae medialis muscle (AMM) *Mandibular adductor muscles (AM, AML1, and AML2) Coracohyomandibularis muscle (CHM) *Depressor hyomandibulae (DH) Constrictor hyoideus ventralis (CHV) Coracobranchiales muscles (CB) *Y muscle (Y) *Z muscle (Z) M muscle (M) Coracohyoideus muscle (CH) *Quadratomandibularis ventral (QV) Muscles of the Cephalic Ventral Region

  8. Objective of the Study: • The researchers attempted to describe the anatomy of the cephalic dorsal and ventral musculature of myliobatoids, as a basis for future phylogenetic genus research.

  9. Methods: • Specimens were collected from areas along the Gulf of Mexico, Gulf of California, and the Pacific Ocean • Larger specimens were dissected in the field • Smaller specimens were fixed in formaldehyde 10% to be transported to a laboratory and dissected at a later time

  10. Methods: • Conventional techniques were used for dissection, focusing on dorsal and ventral cranial musculature Dorsal View Ventral View

  11. Methods: • For each muscle the following characteristics were analyzed: 1. form disposition 2. fiber orientation 3. origin-point of attachment of a muscle; end not easily movable 4. insertion-point of attachment of a muscle; end that is easily movable

  12. Results: Dorsal Musculature • Overall, all taxa was fairly consistent with the exception of some variation in two of the muscles analyzed: 1. Dorsal Longitudinal Bundles 2. Cucullaris Muscle

  13. Results: Dorsal Longitudinal Bundles (DLB) G. Micrura and G. marmorata

  14. Results: Dorsal Longitudinal Bundles (DLB) M. Californica M. munkiana

  15. Results: Cucullaris muscle M. longitostris A. narinari *Absent in A. narinari, M. thurstoni, and M. munkiana

  16. Results: Ventral Musculature • Variations were found in the following muscles: 1. Depressor hyomandibulae 2. Quadratomandibularis muscle 3. Mandibular Adductor 4. Dorsal and Ventral Superficial Constrictor Muscles 5. Coracomandibular Muscle 6. Y muscle 7. Z muscle

  17. Results: Depressor hyomandibulae Reduced in: MC, ML, and AN; Absent in: MM, MT G. micrura M. californica

  18. Results: Quadratomandibularis Muscle • Found only in GMi and GMa • Plesiomorphic Characteristic G. marmorata *Absence of Quad. Muscle considered derived characteristic

  19. Results: Mandibular adductor muscles • Increased size in ML, MC, AN, and RS M. californica G. micrura

  20. Results: Superficial Constrictor Muscles • Reduced in MT and MM • Fused in AN, MC, and ML • Considered synapmorphy G. Marmorata M. Californica M. munkiana

  21. Results: Coracomandibularis Muscle -In MC, Ml, AN, and RS the muscle originates in the pectoral girdle -In GMI, GMA, MT, and MM the muscle originates in the membrane where the coracoarcualis muscle inserts A. narinari M. munkiana

  22. Results: Y muscle and Z muscle • These muscles were found in MC, ML, AN, and RS M. californica

  23. Discussion: • Differences in the ventral musculature are related to feeding habits: • AN, MC, ML, and RS hard-shelled mollusks and crustaceans • MM and MT are filtering species that feed mainly on small crustaceans

  24. Discussion: Phylogenetic Studies Previous Phylogenies

  25. Discussion: Phylogenetic Studies Myliobatids Rhinoptera Mobula Proposed Phylogeny from data of this paper

  26. Conclusions: • Rhinoptera is the myliobatids’ sister group. • The results from this study alone are too general to base a phylogeny on, but the results should be used for future phylogeny research. • Overall, a phylogeny can change drastically depending on what aspect(s) of the specimen a specific study is analyzing.

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