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Haborophocoena minutus
Taxonomy
Haborophocoena minutus was named by Ichishima and Kimura (2009). Its type specimen is SMAC 1388, a partial skull, and it is a 3D body fossil. Its type locality is Haboro, south, which is in a Zanclean coastal mudstone in the Embetsu Formation of Japan.
Synonymy list
| Year | Name and author |
|---|---|
| 2009 | Haborophocoena minutus Ichishima and Kimura p. 857 figs. Fig. 2-6 |
| 2015 | Haborophocoena minutus Colpaert et al. p. 9 figs. Figure 8 |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
†Haborophocoena minutus Ichishima and Kimura 2009
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Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| H. Ichishima and M. Kimura 2009 | Haborophocoena minutus is a relatively small phocoenid for the Early Pliocene. It is
distinguished from Lomacetus, Australithax, Salumiphocaena, and Piscolithax in having the premaxillary foramen lying anteromedial to the premaxillary eminence at the level of the anterior margin of the eminence (this feature is shared with living forms), just posterior to the level of the antorbital notch; from any other phocoenids, living and extinct (except for Piscolithax tedfordi and H. toyoshimai), in having a more posteriorly situated frontal boss at or near the level of the base of the zygomatic process of the squamosal; from any other phocoenid, living and extinct (except for Phocoenoides and H. toyoshimai) in having a relatively small temporal fossa; and from any other phocoenid, living and extinct (except for H. toyoshimai) in having a narrowbased rostrum relative to the supraorbital width. H. minutus differs from H. toyoshimai in that: the skull is absolutely smaller (ca. 80% in parietal width and ca. 72% in cranium length); on the dorsal face of the rostrum the premaxilla makes up less than half the mediolateral width of the rostrum at the level of the antorbital notch; the skull is less skewed; the posteromedial corner of the ascending process of the maxilla is less protruded medially toward the vertex; the curled crest of the maxilla, which is continuous with the posterior premaxillary termination, does not reach the knob-like process of the frontal on the vertex; the premaxillary eminence is lower and flatter; the anterior tip of the prenarial triangular area, on which the nasal plug muscle must have been attached, lies well anterior to the level of the antorbital notch; the lateral wall of the pterygoid sinus fossa formed by the laminae of the palatine and the pterygoid is ventrally much less expanded; a ridge dividing the horizontal lamina from the lateral lamina of the palatine is less sharp and not constricted medially; the temporal fossa is larger: in H. toyoshimai the greatest diameter of the temporal fossa is shorter than the length of the orbit, whereas in H. minutus it is as long as the length of the orbit; the zygomatic process is not tapered anteriorly but rectangular in lateral profile; a distinct ridge divides a fossa on the lateral face of the base of the zygomatic process into dorsal and ventral halves; the angle of the “ectethmoid shields” opposite the horizontal plane of the rostrum is much flatter; the mesethmoid septum that separates the nares from each other is higher posteriorly; and the mesorostral groove attains the maximum width well anterior to the level of the antorbital notch as preserved. The degree of inclination of the long axis of the occipital condyle from the sagittal plane also makes H. minutus (∼30◦) different from H. toyoshimai with a more vertical long axis (∼20◦). |