title: Skull ontogeny and modularity in two species of Lagenorhynchus: Morphological and ecological implications.
abstract: Comparisons of skull shape between closely related species can provide information on the role that phylogeny and function play in cranial evolution. We used 3D-anatomical landmarks in order to study the skull ontogeny of two closely related species, Lagenorhynchus obscurus and Lagenorhynchus australis, with a total sample of 52 skulls. We found shared trends between species, such as the relative compression of the neurocranium and the enlargement of the rostrum during ontogeny. However, these are common mammalian features, associated with prenatal brain development and sensory capsules. Moreover, we found a posterior displacement of the external nares and infraorbital foramina, and a strong development of the rostrum in an anteroposterior direction. Such trends are associated with the process of telescoping and have been observed in postnatal ontogeny of other odontocetes, suggesting a constraint in the pattern. Interspecific differences related to the deepness of facial region, robustness of the feeding apparatus and rostrum orientation may be related with the specific lifestyles of L. obscurus and L. australis. We also tested the presence of three different modules in the skull (basicranium, neurocranium, rostrum), all of which presented strong integration. Only the rostrum showed a different ontogenetic trajectory between species. Even though we detected directional asymmetry, changes in this feature along ontogeny were not detectable. Because asymmetry may be related to echolocation, our results suggest a functional importance of directional asymmetry from the beginning of postnatal life. J. Morphol. 278:203-214, 2017. © 2016 Wiley Periodicals,Inc.
authors.affiliation: Laboratorio de Ecología, Comportamiento y Mamíferos Marinos, División Mastozoología, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Av. Ángel Gallardo 470 (C1405DJR), Buenos Aires, Argentina.|CONICET. Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.
authors.forename: Daniela L
authors.initials: DL
authors.lastname: Del Castillo
authors.affiliation: CONICET. Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.|Instituto Patagónico de Geología y Paleontología, CCT CONICET-CENPAT, Boulevard Brown 2915 (U9120ACD), Puerto Madryn, Chubut, Argentina.
authors.forename: Mariana
authors.initials: M
authors.lastname: Viglino
authors.affiliation: CONICET. Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.|Unidad Ejecutora Lillo, CONICET-Fundación Miguel Lillo, Miguel Lillo 251, Tucumán, 4000, Argentina.|Instituto de Vertebrados, Fundación Miguel Lillo, Miguel Lillo 251 (CP4000), Tucumán, Argentina.
authors.forename: David A
authors.initials: DA
authors.lastname: Flores
authors.affiliation: Laboratorio de Ecología, Comportamiento y Mamíferos Marinos, División Mastozoología, Museo Argentino de Ciencias Naturales "Bernardino Rivadavia", Av. Ángel Gallardo 470 (C1405DJR), Buenos Aires, Argentina.|CONICET. Consejo Nacional de Investigaciones Científicas y Técnicas, Argentina.|Centro de Estudios Biomédicos, Biotecnológicos, Ambientales y Diagnóstico, Departamento de Ciencias Naturales y Antropología, Fundación Azara, Universidad Maimonides, Hidalgo 775 7mo (C1405BDB), Buenos Aires, Argentina.
authors.forename: Humberto L
authors.initials: HL
authors.lastname: Cappozzo
mesh_terms: D000818:Animals; D005075:Biological Evolution; D004289:Dolphins / Q000033:anatomy & histology*; D004463:Ecology; D010802:Phylogeny; D012886:Skull / Q000033:anatomy & histology*
keywords: Delphinidae; Lagenorhynchus; directional asymmetry; geometric morphometrics; modularity; ontogeny