Anatomical Comparison of Anatomical Comparison of the Cephalic Musculature of the Cephalic Musculature of

Some Members of the Some Members of the Superfamily Myliobatoidea Superfamily Myliobatoidea

(Chondrichthyes): (Chondrichthyes): Implications for Evolutionary Implications for Evolutionary

UnderstandingUnderstanding

Gonzalez-Isais M. 2003. Anatomical Gonzalez-Isais M. 2003. Anatomical Comparison of the Cephalic Musculature of Comparison of the Cephalic Musculature of

Some Members of the Superfamily Some Members of the Superfamily Myliobatoidea (Chondrichthyes): Implications Myliobatoidea (Chondrichthyes): Implications

for Evolutionary Understanding. for Evolutionary Understanding. The Anatomical The Anatomical Record Part A Record Part A 271A: 259-272. 271A: 259-272.

Background Information: Background Information:

© Tracy Clarkhttp://www.divebums.com/FishID/Pages/butterfly_ray.html

Myliobatoidea

Myliobatoidea Species Myliobatoidea Species Studied:Studied:

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

Gymnura marmorata (GMA)

California Butterfly Ray

http://www.fishbase.org

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

http://www.fishbase.org

Http://www.fishbase.org

Myliobatis californica (MC)Bat Eagle Ray

Myliobatis longirostris (ML)Snouted Eagle Ray

Rhinoptera steindachneri (RS)Pacific Cownose Ray

Muscles of the Muscles of the DorsalDorsal Cephalic Cephalic RegionRegion

• Precranial muscle (PM)Precranial muscle (PM)

• Ethmoideo-parethmoidalis muscle (EPE)Ethmoideo-parethmoidalis muscle (EPE)

• *Dorsal longitudinal bundles (DLB)*Dorsal longitudinal bundles (DLB)

• Levator hyomandibulae muscle (LHM)Levator hyomandibulae muscle (LHM)

• Levator spiracularis muscle (LS)Levator spiracularis muscle (LS)

• Superficial dorsal constrictor muscles 1-Superficial dorsal constrictor muscles 1-5 (DC1-DC5)5 (DC1-DC5)

• Constrictor hyoideus dorsalis (CHD)Constrictor hyoideus dorsalis (CHD)

• *Cucullaris muscle (CC)*Cucullaris muscle (CC)

Muscles of the Cephalic Muscles of the Cephalic VentralVentral RegionRegion

• Depressor rostri muscle Depressor rostri muscle (DR)(DR)

• *Superficial*Superficial transverse transverse (ST) muscle and (ST) muscle and superficial ventral superficial ventral constrictorsconstrictors (VC1-VC5) (VC1-VC5)

• Coracoarcualis muscle Coracoarcualis muscle (CA)(CA)

• *Coracomandibular *Coracomandibular muscle (CM)muscle (CM)

• Suborbitalis muscle (SB)Suborbitalis muscle (SB)• Adductor mandibulae Adductor mandibulae

medialis muscle (AMM)medialis muscle (AMM)• *Mandibular adductor *Mandibular adductor

muscles (AM, AML1, muscles (AM, AML1, and AML2)and AML2)

• Coracohyomandibularis Coracohyomandibularis muscle (CHM)muscle (CHM)

• *Depressor *Depressor hyomandibulae (DH)hyomandibulae (DH)

• Constrictor hyoideus Constrictor hyoideus ventralis (CHV)ventralis (CHV)

• Coracobranchiales Coracobranchiales muscles (CB)muscles (CB)

• *Y muscle (Y)*Y muscle (Y)• *Z muscle (Z)*Z muscle (Z)• M muscle (M)M muscle (M)• Coracohyoideus muscle Coracohyoideus muscle

(CH)(CH)• *Quadratomandibula*Quadratomandibula

ris ventral (QV)ris ventral (QV)

Objective of the Study:Objective of the Study:

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

Methods:Methods:

• Specimens were collected from areas Specimens were collected from areas along the Gulf of Mexico, Gulf of along the Gulf of Mexico, Gulf of California, and the Pacific OceanCalifornia, and the Pacific Ocean

• Larger specimens were dissected in Larger specimens were dissected in the fieldthe field

• Smaller specimens were fixed in Smaller specimens were fixed in formaldehyde 10% to be transported formaldehyde 10% to be transported to a laboratory and dissected at a to a laboratory and dissected at a later timelater time

Methods:Methods:

• Conventional techniques were used for Conventional techniques were used for dissection, focusing on dorsal and ventral dissection, focusing on dorsal and ventral cranial musculaturecranial musculature

Dorsal View Ventral View

Methods:Methods:

• For each muscle the following For each muscle the following characteristics were analyzed:characteristics were analyzed:1. form disposition1. form disposition2. fiber orientation2. fiber orientation3. 3. originorigin-point of attachment of a -point of attachment of a muscle; end not easily movable muscle; end not easily movable 4. 4. insertioninsertion-point of attachment of a-point of attachment of a muscle; end that is easily movable muscle; end that is easily movable

Results:Results:Dorsal MusculatureDorsal Musculature

• Overall, all taxa was fairly consistent Overall, all taxa was fairly consistent with the exception of some variation with the exception of some variation in two of the muscles analyzed:in two of the muscles analyzed:

1. Dorsal Longitudinal Bundles1. Dorsal Longitudinal Bundles

2. Cucullaris Muscle2. Cucullaris Muscle

Results:Results: Dorsal Longitudinal Bundles Dorsal Longitudinal Bundles (DLB)(DLB)

G. Micrura and G. marmorata

Results:Results: Dorsal Longitudinal Bundles Dorsal Longitudinal Bundles (DLB)(DLB)

M. Californica M. munkiana

Results:Results:Cucullaris muscleCucullaris muscle

A. narinari M. longitostris

*Absent in A. narinari, M. thurstoni, and M. munkiana

Results:Results:Ventral MusculatureVentral Musculature

• Variations were found in the following Variations were found in the following muscles:muscles:

1. Depressor hyomandibulae1. Depressor hyomandibulae2. Quadratomandibularis muscle2. Quadratomandibularis muscle3. Mandibular Adductor3. Mandibular Adductor4. Dorsal and Ventral Superficial 4. Dorsal and Ventral Superficial

ConstrictorConstrictor Muscles Muscles5. Coracomandibular Muscle5. Coracomandibular Muscle6. Y muscle6. Y muscle7. Z muscle7. Z muscle

Results:Results:Depressor hyomandibulaeDepressor hyomandibulae

Reduced in: MC, ML, and AN; Absent in: MM, MT

G. micrura M. californica

Results:Results:Quadratomandibularis Quadratomandibularis

MuscleMuscle

• Found only in Found only in GMi and GMaGMi and GMa– Plesiomorphic Plesiomorphic

CharacteristicCharacteristic

*Absence of Quad. Muscle considered derived characteristic*Absence of Quad. Muscle considered derived characteristic

G. marmorata

Results:Results:Mandibular adductor Mandibular adductor

musclesmuscles• Increased size in ML, MC, AN, and RSIncreased size in ML, MC, AN, and RS

M. californica G. micrura

Results:Results:Superficial Constrictor Superficial Constrictor

MusclesMuscles• Reduced in MT and MMReduced in MT and MM

• Fused in AN, MC, and MLFused in AN, MC, and ML– Considered synapmorphy Considered synapmorphy

G. Marmorata

M. munkianaM. Californica

Results:Results:Coracomandibularis MuscleCoracomandibularis Muscle

A. narinari M. munkiana

-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

Results:Results:Y muscle and Z muscleY muscle and Z muscle

• These muscles were found in MC, ML, AN, These muscles were found in MC, ML, AN, and RSand RS

M. californica

Discussion:Discussion:

• Differences in the ventral musculature Differences in the ventral musculature are related to feeding habits:are related to feeding habits:– AN, MC, ML, and RS hard-shelled mollusks AN, MC, ML, and RS hard-shelled mollusks

and crustaceansand crustaceans– MM and MT are filtering species that feed MM and MT are filtering species that feed

mainly on small crustaceansmainly on small crustaceans

Discussion:Discussion:Phylogenetic StudiesPhylogenetic Studies

Previous Phylogenies

Discussion:Discussion:Phylogenetic StudiesPhylogenetic Studies

Myliobatids

Rhinoptera

Mobula

Proposed Phylogeny from

data of this paper

Conclusions:Conclusions:

1.1. RhinopteraRhinoptera is the myliobatids’ sister group. is the myliobatids’ sister group.

2.2. The results from this study alone are too The results from this study alone are too general to base a phylogeny on, but the general to base a phylogeny on, but the results should be used for future phylogeny results should be used for future phylogeny research.research.

3.3. Overall, a phylogeny can change drastically Overall, a phylogeny can change drastically depending on what aspect(s) of the depending on what aspect(s) of the specimen a specific study is analyzing.specimen a specific study is analyzing.