Most of the diversity of extant southern true seals (Phocidae: Monachinae) is present in the Southern Ocean, but a poor fossil record means that the origin of this fauna remains unknown. Australia represents a large gap in the record bordering the Southern Ocean that could possibly inform on the origins of the extant Antarctic monachines, with most known fossils remaining undescribed. Here we describe the oldest Australian fossil pinniped assemblage, from the Late Miocene to the Early Pliocene of Beaumaris. Two fossils are referrable to Pinnipedia, five (possibly six) to Phocidae and a humerus is referrable to Monachinae. The humerus is not referrable to any extant tribe, potentially representing an archaic monachine. The description of this assemblage is consistent with the Neogene pinniped fauna of Australia being exclusively monachine before the arrival of otariids (fur seals and sea lions). The Beaumaris humerus, along with other Neogene phocids from the Southern Ocean margins, were smaller than their extant Antarctic relatives, possibly driven by longer food chains with less energy efficiency between trophic levels. This suggests that small archaic phocids potentially used the Southern Ocean as a means of dispersal before the arrival of extant Antarctic monachines.

中文翻译：

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小型Phophidae在古代南部海洋的殖民：澳大利亚的新证据

现存的南方真海豹的大多数物种（Phocidae：Monachinae）都存在于南大洋中，但是化石记录不佳意味着该动物的起源仍然未知。在与南大洋接壤的记录中，澳大利亚代表着很大的差距，这可能可以为现存的南极单核龙的起源提供信息，而最著名的化石仍未描述。在这里，我们描述了从中新世晚期到波马里斯早期上新世的最古老的澳大利亚化石pin夹组合。Pinnipedia有两种化石，Phocidae有五种（可能是六种），Monachinae有肱骨。肱骨不能与任何现存的部落相提并论，可能代表着古老的莫纳辛人。这种组合的描述与澳大利亚新近代捏捏的动物在OTARIID（海狗和海狮）到来之前仅是莫纳辛胺相一致。博马里斯人的肱骨以及其他来自南大洋边缘的新近纪生辉石都比它们现存的南极亲戚小，这可能是由于食物链较长，营养级之间的能源效率较低所致。这表明，在现存的南极莫纳克山脉到来之前，小的古古堡可能利用了南大洋作为扩散的手段。