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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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Related in: MedlinePlus

Left, 6A-B, and right, 6C-D, lateral views of referred specimen of Nanokogia isthmia gen. et sp. nov. (UF 273554).Abbreviations: boc, basioccipital crest; eam, external auditory meatus; eo, exoccipital; fr, frontal; lmc, lateral maxillary crest; mx, maxilla; npp, notch for posterior process of tympanic; oc, occipital condyle; of, optic foramen; pa, parietal; pmx, premaxilla; pop, postorbital process; prp, preorbital process; prs, presphenoid; ptdl, dorsal lamina of pterygoid; ptml, medial lamina of pterygoid; scb, supracranial basin; smc, supramastoid crest; sq, squamosal; tc, temporal crest; vo, vomer; zp, zygomatic process. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.
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pone.0123909.g007: Left, 6A-B, and right, 6C-D, lateral views of referred specimen of Nanokogia isthmia gen. et sp. nov. (UF 273554).Abbreviations: boc, basioccipital crest; eam, external auditory meatus; eo, exoccipital; fr, frontal; lmc, lateral maxillary crest; mx, maxilla; npp, notch for posterior process of tympanic; oc, occipital condyle; of, optic foramen; pa, parietal; pmx, premaxilla; pop, postorbital process; prp, preorbital process; prs, presphenoid; ptdl, dorsal lamina of pterygoid; ptml, medial lamina of pterygoid; scb, supracranial basin; smc, supramastoid crest; sq, squamosal; tc, temporal crest; vo, vomer; zp, zygomatic process. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.

Mentions: On the rostrum, the maxilla reaches the distal tip, together with the premaxilla and the vomer (c. 2[1]). When viewed dorsally, the lateral borders of the rostral portion of the maxilla taper anteriorly with a marked constriction at about mid-length, its width diminishing anteriorly and becoming narrower in dorsal view than the premaxilla anteriorly (c. 4[1], 5[0]). Along the rostrum, the dorsal surface of the maxilla is flat to convex, especially in the area anteromedial and medial to the antorbital notches. The antorbital notches are deep, narrow slits (c. 9[2]) entering the supracranial basin (c. 10[1]), as in Praekogia and Kogia. Posterior to the antorbital notches, the maxillae are greatly expanded over the cranial roof, covering nearly all of the frontals, and forming the supracranial basin (c. 3[1], 21[1]) (Figs 2, 11, 14 and S2 Fig). The outline of the supracranial basin is oval, similar to that of Praekogia and contrasting with the more rounded outline of Kogia. The lateral maxillary crests are high, with rounded to sharp, medially recurved dorsal margins that slightly overhang the basin, similar to Praekogia and differing from the more inflated crests of Kogia and the thinner crests of Aprixokogia. The lateral maxillary crests of Nanokogia reach a maximum height and width of about 20 mm at the level of the antorbital notches; posteriorly the crests diminish in height and thickness (reaching a minimum of ~ 5 mm). Posterolaterally the maxillary crests overhang the temporal fossa and occipital region (Figs 2, 4, 6 and 7). Medially, the left maxilla joins the right premaxilla and forms part of the anterior half of the sagittal facial crest as in Praekogia [11] (Figs 2, 11C, 11D, 14C, 14D and S2C–S2D Fig); this condition contrasts with that of Kogia where the maxilla forms part of the sagittal facial crest throughout its length [29] (Figs 11E, 11F, 14E, 14F and S2 Fig). On the surface of the supracranial basin, posterolateral to the right external naris, there is a large, kidney-shaped fossa, herein termed supracranial fossa (= premaxillary fossa of Barnes [11]). The deepest part of this fossa is towards its anteromedial edge, where it reaches a maximum depth of about 2 cm; posteriorly it becomes shallower. A similar fossa is present in Praekogia cedrosensis and Aprixokogia kelloggi. However, in Praekogia the fossa is floored by both the premaxilla and maxilla, whereas in Nanokogia, as in Aprixokogia, it seems to be formed solely by the maxilla. The supracranial fossa of Aprixokogia differs from Nanokogia and Praekogia in that it extends further posteromedially (Figs 11, 14 and S2 Fig). On the right maxilla of Nanokogia there are at least three small, dorsal infraorbital foramina (c. 11[0]). The single anterior dorsal infraorbital foramen is located anteromedial to the antorbital notch, is rounded, and has a diameter of about 5 mm. There are also at least two posterior dorsal infraorbital foramina. The largest of these is located posteromedial to the antorbital notch, is rounded, and has a diameter of about 6 mm. The second foramen is located near the anterolateral edge of the supracranial fossa, has a smaller diameter (<5 mm), and continues posterolaterally as a shallow groove along the edge of the fossa. A similar foramen is also observed in Praekogia cedrosensis [11] (Figs 2 and 11C). The left maxilla has at least two posterior dorsal infraorbital foramina (Figs 2 and 14D). Both foramina are located posterolateral to the external nares; the anteriormost is the smallest (<5 mm in diameter) and opens anteromedially whereas the second is larger (~7 mm in diameter) and opens dorsally. On the left maxilla of the referred specimen, UF 273554, a single dorsal infraorbital foramen is preserved. It is located posterodorsal to the left external naris, opens laterally, and is anteroposteriorly longer than dorsoventrally wide (~1.5 cm long by 0.5 cm wide (Fig 4A and 4B).


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)

Left, 6A-B, and right, 6C-D, lateral views of referred specimen of Nanokogia isthmia gen. et sp. nov. (UF 273554).Abbreviations: boc, basioccipital crest; eam, external auditory meatus; eo, exoccipital; fr, frontal; lmc, lateral maxillary crest; mx, maxilla; npp, notch for posterior process of tympanic; oc, occipital condyle; of, optic foramen; pa, parietal; pmx, premaxilla; pop, postorbital process; prp, preorbital process; prs, presphenoid; ptdl, dorsal lamina of pterygoid; ptml, medial lamina of pterygoid; scb, supracranial basin; smc, supramastoid crest; sq, squamosal; tc, temporal crest; vo, vomer; zp, zygomatic process. 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.g007: Left, 6A-B, and right, 6C-D, lateral views of referred specimen of Nanokogia isthmia gen. et sp. nov. (UF 273554).Abbreviations: boc, basioccipital crest; eam, external auditory meatus; eo, exoccipital; fr, frontal; lmc, lateral maxillary crest; mx, maxilla; npp, notch for posterior process of tympanic; oc, occipital condyle; of, optic foramen; pa, parietal; pmx, premaxilla; pop, postorbital process; prp, preorbital process; prs, presphenoid; ptdl, dorsal lamina of pterygoid; ptml, medial lamina of pterygoid; scb, supracranial basin; smc, supramastoid crest; sq, squamosal; tc, temporal crest; vo, vomer; zp, zygomatic process. Gray shaded areas indicate sediment; diagonal lines denote broken surfaces.
Mentions: On the rostrum, the maxilla reaches the distal tip, together with the premaxilla and the vomer (c. 2[1]). When viewed dorsally, the lateral borders of the rostral portion of the maxilla taper anteriorly with a marked constriction at about mid-length, its width diminishing anteriorly and becoming narrower in dorsal view than the premaxilla anteriorly (c. 4[1], 5[0]). Along the rostrum, the dorsal surface of the maxilla is flat to convex, especially in the area anteromedial and medial to the antorbital notches. The antorbital notches are deep, narrow slits (c. 9[2]) entering the supracranial basin (c. 10[1]), as in Praekogia and Kogia. Posterior to the antorbital notches, the maxillae are greatly expanded over the cranial roof, covering nearly all of the frontals, and forming the supracranial basin (c. 3[1], 21[1]) (Figs 2, 11, 14 and S2 Fig). The outline of the supracranial basin is oval, similar to that of Praekogia and contrasting with the more rounded outline of Kogia. The lateral maxillary crests are high, with rounded to sharp, medially recurved dorsal margins that slightly overhang the basin, similar to Praekogia and differing from the more inflated crests of Kogia and the thinner crests of Aprixokogia. The lateral maxillary crests of Nanokogia reach a maximum height and width of about 20 mm at the level of the antorbital notches; posteriorly the crests diminish in height and thickness (reaching a minimum of ~ 5 mm). Posterolaterally the maxillary crests overhang the temporal fossa and occipital region (Figs 2, 4, 6 and 7). Medially, the left maxilla joins the right premaxilla and forms part of the anterior half of the sagittal facial crest as in Praekogia [11] (Figs 2, 11C, 11D, 14C, 14D and S2C–S2D Fig); this condition contrasts with that of Kogia where the maxilla forms part of the sagittal facial crest throughout its length [29] (Figs 11E, 11F, 14E, 14F and S2 Fig). On the surface of the supracranial basin, posterolateral to the right external naris, there is a large, kidney-shaped fossa, herein termed supracranial fossa (= premaxillary fossa of Barnes [11]). The deepest part of this fossa is towards its anteromedial edge, where it reaches a maximum depth of about 2 cm; posteriorly it becomes shallower. A similar fossa is present in Praekogia cedrosensis and Aprixokogia kelloggi. However, in Praekogia the fossa is floored by both the premaxilla and maxilla, whereas in Nanokogia, as in Aprixokogia, it seems to be formed solely by the maxilla. The supracranial fossa of Aprixokogia differs from Nanokogia and Praekogia in that it extends further posteromedially (Figs 11, 14 and S2 Fig). On the right maxilla of Nanokogia there are at least three small, dorsal infraorbital foramina (c. 11[0]). The single anterior dorsal infraorbital foramen is located anteromedial to the antorbital notch, is rounded, and has a diameter of about 5 mm. There are also at least two posterior dorsal infraorbital foramina. The largest of these is located posteromedial to the antorbital notch, is rounded, and has a diameter of about 6 mm. The second foramen is located near the anterolateral edge of the supracranial fossa, has a smaller diameter (<5 mm), and continues posterolaterally as a shallow groove along the edge of the fossa. A similar foramen is also observed in Praekogia cedrosensis [11] (Figs 2 and 11C). The left maxilla has at least two posterior dorsal infraorbital foramina (Figs 2 and 14D). Both foramina are located posterolateral to the external nares; the anteriormost is the smallest (<5 mm in diameter) and opens anteromedially whereas the second is larger (~7 mm in diameter) and opens dorsally. On the left maxilla of the referred specimen, UF 273554, a single dorsal infraorbital foramen is preserved. It is located posterodorsal to the left external naris, opens laterally, and is anteroposteriorly longer than dorsoventrally wide (~1.5 cm long by 0.5 cm wide (Fig 4A and 4B).

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