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Evolutionary Patterns among Living and Fossil Kogiid Sperm Whales: Evidence from the Neogene of Central America.

Velez-Juarbe J, Wood AR, De Gracia C, Hendy AJ - PLoS ONE (2015)

Bottom Line: However, this organ is much reduced in kogiids and may have become functionally different.Furthermore our results show that reduction of the spermaceti organ has occurred iteratively in kogiids, once in Thalassocetus antwerpiensis in the early-middle Miocene, and more recently in Kogia spp.Finally, comparison of Nanokogia with the coeval Scaphokogia cochlearis from Peru shows that these two species display a greater morphological disparity between them than that observed between the extant members of the group.

View Article: PubMed Central - PubMed

Affiliation: Department of Mammalogy, Natural History Museum of Los Angeles County, Los Angeles, California, United States of America; John D. Cooper Archaeological and Paleontological Center, Department of Geological Sciences, California State University, Fullerton, California, United States of America.

ABSTRACT
Kogiids are known by two living species, the pygmy and dwarf sperm whale (Kogia breviceps and K. sima). Both are relatively rare, and as their names suggest, they are closely related to the sperm whale, all being characterized by the presence of a spermaceti organ. However, this organ is much reduced in kogiids and may have become functionally different. Here we describe a fossil kogiid from the late Miocene of Panama and we explore the evolutionary history of the group with special attention to this evolutionary reduction. The fossil consists of cranial material from the late Tortonian (~7.5 Ma) Piña facies of the Chagres Formation in Panama. Detailed comparison with other fossil and extant kogiids and the results of a phylogenetic analysis place the Panamanian kogiid, herein named Nanokogia isthmia gen. et sp. nov., as a taxon most closely related to Praekogia cedrosensis from the Messinian (~6 Ma) of Baja California and to Kogia spp. Furthermore our results show that reduction of the spermaceti organ has occurred iteratively in kogiids, once in Thalassocetus antwerpiensis in the early-middle Miocene, and more recently in Kogia spp. Additionally, we estimate the divergence between extant species of Kogia at around the late Pliocene, later than previously predicted by molecular estimates. Finally, comparison of Nanokogia with the coeval Scaphokogia cochlearis from Peru shows that these two species display a greater morphological disparity between them than that observed between the extant members of the group. We hypothesize that this reflects differences in feeding ecologies of the two species, with Nanokogia being more similar to extant Kogia. Nanokogia shows that kogiids have been part of the Neotropical marine mammal communities at least since the late Miocene, and gives us insight into the evolutionary history and origins of one of the rarest groups of living whales.

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Dorsal view of holotype skull of Nanokogia isthmia gen. et sp. nov. (UF 280000).Abbreviations: adif, anterior dorsal infraorbital foramen; an, antorbital notch; en, external nares; et, ethmoid; fr, frontal; la+j, lacrimal + jugal; lmc, lateral maxillary crest; mrg, mesorostral groove; mx, maxilla; pmx, premaxilla; pdif, posterior dorsal infraorbital foramen; scf, supracranial fossa; sfc, sagittal facial crest; sq, squamosal; vo, vomer. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.
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pone.0123909.g002: Dorsal view of holotype skull of Nanokogia isthmia gen. et sp. nov. (UF 280000).Abbreviations: adif, anterior dorsal infraorbital foramen; an, antorbital notch; en, external nares; et, ethmoid; fr, frontal; la+j, lacrimal + jugal; lmc, lateral maxillary crest; mrg, mesorostral groove; mx, maxilla; pmx, premaxilla; pdif, posterior dorsal infraorbital foramen; scf, supracranial fossa; sfc, sagittal facial crest; sq, squamosal; vo, vomer. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.

Mentions: Description of the skull is based on both the holotype (UF 280000) and the referred specimen (UF 273554) (Figs 2–9, 10–14 and S1–S2 Figs). Because in the temporal and occipital regions the relationships between the different bones are not clear we treat these as separate subdivisions below in the description instead of the individual bones. The holotype is a nearly complete skull, missing parts of the basicranium and parts of the posterolateral surface of the skull. The referred specimen is missing the rostrum, the right supraorbital process and the right half of the supracranial basin. The skull of Nanokogia is small (c. 8[0]) (Table 1), asymmetric, with a short rostrum (c. 1[2]) that tapers distally, not gradually as in Kogia, and has a marked constriction at about the middle of its length (Figs 2 and 3). The distal end of the rostrum is squared off, not pointed as in Kogia, nor cylindrical as in Scaphokogia, nor rounded as in Aprixokogia. Sutures are fused on both skulls, indicating that they belonged to adult individuals.


Evolutionary Patterns among Living and Fossil Kogiid Sperm Whales: Evidence from the Neogene of Central America.

Velez-Juarbe J, Wood AR, De Gracia C, Hendy AJ - PLoS ONE (2015)

Dorsal view of holotype skull of Nanokogia isthmia gen. et sp. nov. (UF 280000).Abbreviations: adif, anterior dorsal infraorbital foramen; an, antorbital notch; en, external nares; et, ethmoid; fr, frontal; la+j, lacrimal + jugal; lmc, lateral maxillary crest; mrg, mesorostral groove; mx, maxilla; pmx, premaxilla; pdif, posterior dorsal infraorbital foramen; scf, supracranial fossa; sfc, sagittal facial crest; sq, squamosal; vo, vomer. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4414568&req=5

pone.0123909.g002: Dorsal view of holotype skull of Nanokogia isthmia gen. et sp. nov. (UF 280000).Abbreviations: adif, anterior dorsal infraorbital foramen; an, antorbital notch; en, external nares; et, ethmoid; fr, frontal; la+j, lacrimal + jugal; lmc, lateral maxillary crest; mrg, mesorostral groove; mx, maxilla; pmx, premaxilla; pdif, posterior dorsal infraorbital foramen; scf, supracranial fossa; sfc, sagittal facial crest; sq, squamosal; vo, vomer. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.
Mentions: Description of the skull is based on both the holotype (UF 280000) and the referred specimen (UF 273554) (Figs 2–9, 10–14 and S1–S2 Figs). Because in the temporal and occipital regions the relationships between the different bones are not clear we treat these as separate subdivisions below in the description instead of the individual bones. The holotype is a nearly complete skull, missing parts of the basicranium and parts of the posterolateral surface of the skull. The referred specimen is missing the rostrum, the right supraorbital process and the right half of the supracranial basin. The skull of Nanokogia is small (c. 8[0]) (Table 1), asymmetric, with a short rostrum (c. 1[2]) that tapers distally, not gradually as in Kogia, and has a marked constriction at about the middle of its length (Figs 2 and 3). The distal end of the rostrum is squared off, not pointed as in Kogia, nor cylindrical as in Scaphokogia, nor rounded as in Aprixokogia. Sutures are fused on both skulls, indicating that they belonged to adult individuals.

Bottom Line: However, this organ is much reduced in kogiids and may have become functionally different.Furthermore our results show that reduction of the spermaceti organ has occurred iteratively in kogiids, once in Thalassocetus antwerpiensis in the early-middle Miocene, and more recently in Kogia spp.Finally, comparison of Nanokogia with the coeval Scaphokogia cochlearis from Peru shows that these two species display a greater morphological disparity between them than that observed between the extant members of the group.

View Article: PubMed Central - PubMed

Affiliation: Department of Mammalogy, Natural History Museum of Los Angeles County, Los Angeles, California, United States of America; John D. Cooper Archaeological and Paleontological Center, Department of Geological Sciences, California State University, Fullerton, California, United States of America.

ABSTRACT
Kogiids are known by two living species, the pygmy and dwarf sperm whale (Kogia breviceps and K. sima). Both are relatively rare, and as their names suggest, they are closely related to the sperm whale, all being characterized by the presence of a spermaceti organ. However, this organ is much reduced in kogiids and may have become functionally different. Here we describe a fossil kogiid from the late Miocene of Panama and we explore the evolutionary history of the group with special attention to this evolutionary reduction. The fossil consists of cranial material from the late Tortonian (~7.5 Ma) Piña facies of the Chagres Formation in Panama. Detailed comparison with other fossil and extant kogiids and the results of a phylogenetic analysis place the Panamanian kogiid, herein named Nanokogia isthmia gen. et sp. nov., as a taxon most closely related to Praekogia cedrosensis from the Messinian (~6 Ma) of Baja California and to Kogia spp. Furthermore our results show that reduction of the spermaceti organ has occurred iteratively in kogiids, once in Thalassocetus antwerpiensis in the early-middle Miocene, and more recently in Kogia spp. Additionally, we estimate the divergence between extant species of Kogia at around the late Pliocene, later than previously predicted by molecular estimates. Finally, comparison of Nanokogia with the coeval Scaphokogia cochlearis from Peru shows that these two species display a greater morphological disparity between them than that observed between the extant members of the group. We hypothesize that this reflects differences in feeding ecologies of the two species, with Nanokogia being more similar to extant Kogia. Nanokogia shows that kogiids have been part of the Neotropical marine mammal communities at least since the late Miocene, and gives us insight into the evolutionary history and origins of one of the rarest groups of living whales.

Show MeSH
Related in: MedlinePlus