Belongs within: Carnivora.
Contains: Phocinae.
The Phocidae, true seals, are one of the two lineages within the Pinnipedia. In contrast to the eared seals of the Otarioidea, phocids lack external ear flaps, and are unable to bring the hind flippers underneath the body for walking on land. Living phocids are divided between the subfamilies Phocinae and Monachinae, with monachines having the claws on the hind flippers much reduced. Monachinae are more diverse in the Southern Hemisphere, being represented in the Northern Hemisphere by the monk seals Monachus and the northern elephant seal Mirounga angustirostris. The elephant seals Mirounga are the largest living carnivorans with the largest individuals reaching weights of about four tonnes. The monk seals are found in warm waters and have short, broad, flat snouts.
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Published 19 July 2007
This page’s subject is the Phocidae, the earless or ‘true’ seals. Phocidae are quite easily distinguishable from the Otariidae (sea lions and fur seals) by the absence of external ears (hence the name, duh) and the inability to turn their hind flippers under the body and use them in locomotion out of the water. This means that while otariids are still reasonably mobile on land, phocids are decidedly clumsy critters, reduced to a sort of humping, slug-like movement (Wikipedia claims that this is referred to as galumphing, after the usage in Carroll [he left it dead, and with its head, he went galumphing back] and admit that I’d always imagined galumphing slightly differently—some of you may even recall the performance of The Jabberwocky on an episode of The Muppet Show, where Scooter rendered galumphing as a sort of jerky stomp with the word ‘galumph’ intoned at every step). Put them in the water, though, and phocids are magical.
The Phocidae are divided into two subfamilies, the ‘Northern Hemisphere’ Phocinae and the ‘Southern Hemisphere’ Monachinae. The inverted commas are there because the Monachinae do include a small number of Northern Hemisphere species, including the type genus Monachus, the monk seals, and the northern elephant seal Mirounga angustirostris. While it has been suggested in the past that Monachinae might be paraphyletic with regard to Phocinae (reported in Walsh & Naish 2002), modern studies both molecular and morphological are fairly unanimous that the two subfamilies are monophyletic (Arnason et al. 2006; Davis et al. 2004).
The Monachinae probably aren’t as speciose as the Phocinae (it’s a little difficult to tell, as the number of species in the Phocinae goes up and down from reviewer to reviewer) but are arguably more diverse in form. Living species are divided into three tribes—Monachini (Monachus), Miroungini (Mirounga, the elephant seals) and Lobodontini (Antarctic seals). The first two tribes only include one genus each in the modern fauna but also include fossil genera.
Monachus (the monk seals) is the basalmost clade of monachines, and the only tropical/subtropical genus of Phocidae. There are three species with widely separated distributions—one each in the Mediterranean (Monachus monachus), Caribbean (M. tropicalis) and Hawaii (M. schauinslandi), though the Caribbean species is now extinct and the other two are endangered. Most references to monk seals I’ve come across mention their small size, but the Monachus Guardian website indicates that all are over two metres in length, demonstrating once again that size is a relative thing.
Mirounga are the two elephant seals—the Northern Pacific Mirounga angustirostris and the circum-Antarctic M. leonina. Elephant seals are so-called for two reasons—the males have a large inflatable proboscis that is used to make loud roaring noises, and because they are absolutely huge. Indeed, they are the largest living carnivorans. Wikipedia cites a size of nearly 2.3 tonnes, with a recorded maximum of 5 tonnes. Elephant seals are also the most terrestrially capable of all Phocidae (Walsh & Naish 2002). Back in New Zealand, elephant seals make the news every few years or so when one makes its way inland, including one dubbed ‘Humphrey’ that was present intermittently over a period of five years and was famed for his attachment to a herd of cows. Fantastic quote of the day about elephant seals inland—”Although popular with locals and visitors, the impact of an amorous, two tonne male elephant seal on cars and other structures is significant” (Harcourt 2001).
The Lobodontini are the most diverse group of monachines, including the crabeater seal Lobodon carcinophagus, Weddell seal Leptonychotes weddellii, leopard seal Hydrurga leptonyx and Ross seal Ommatophoca rossi. The Ross seal is a particularly obscure animal, little seen and restricted to the Antarctic. The leopard seal is the real star member of this group, though—a sleek super-predator that can be over 3.5m long and 400kg, able to eliminate about 2.5% of an Adelie penguin colony in a single season (Harcourt 2001—that’s leopard seals as a whole, of course, not a single individual). Hydrurga is also known for its ability to extend its neck quite some distance from its body. Notably from this factoid, it is probably closely related to the fossil long-necked seal Acrophoca, inspiration of a whole swath of lake-monster theories.
Systematics of Phocidae
Synapomorphies (from Tedford 1976): Aquatic, swimming mainly by flexion of trunk; dentition reduced to homodonty; enlarged teres process for teres major muscle which occupies its lateral border.
<==Phocidae [Cystophorinae] | i. s.: Palmidophoca Ginsburg & Janvier 1975SM93 | `--P. callirhoe Ginsburg & Janvier 1975BDR85 | Praepusa Kretzoi 1941SM93 | `--P. pannonicaG76 | Monachopsis Kretzoi 1941SM93 | Properiptychus Ameghino 1897SM93 |--Semantorinae [Semantoridae]T76 | |--SemantorT76 | `--Potamotherium Geoffroy 1833T76, D07 | `--P. valetoniG76 `--+--PhocinaeFS15 `--Monachinae [Lobodontinae]AG06 | i. s.: Monotherium Van Beneden 1876R76, SM93 | |--M. aberratumR76 | |--M. affineR76 | |--M. delogniiR76 | |--M. gaudiniR76 | |--M. maeoticum [=Phoca maeotica]R76 | `--M. wymaniR76 | Pliophoca etruscaR76 | Piscophoca pacifica de Muizon 1981BDR85 | CallophocaR76 | |--C. ambigua [=Mesotaria ambigua]R76 | `--C. obscuraR76 | Pristiphoca occitanaR76 | Properiptychus argentinus Ameghino 1893BDR85 |--+--Messiphoca mauretanica de Muizon 1981BDR85 | `--Monachus Fleming 1822FS15, BR05 [Monachini] | |--M. monachusFS15 | `--+--M. schauinslandiFS15 | `--M. tropicalisFS15 `--+--Mirounga Gray in Griffith 1827FS15, C57 (see below for synonymy) | |--M. leonina (Linnaeus 1758) (see below for synonymy)C57 | `--M. angustirostrisFS15 `--LobodontiniAG06 |--Ommatophoca Gray 1844FS15, C57 | `--*O. rossii Gray 1844C57 `--+--+--Lobodon Gray 1844FS15, C57 | | `--*L. carcinophagus (Jacquinot & Pucheran 1842) (see below for synonymy)C57 | `--Homiphoca de Muizon & Hendley 1980BDR85 | `--*H. capensis (Hendey & Repenning 1972) [=Prionodelphis capensis]BDR85 `--+--Leptonychotes Gill 1872FS15, C57 [incl. Poecilophoca Flower & Lydekker 1891C57] | `--*L. weddellii (Lesson 1826) (see below for synonymy)C57 `--+--Acrophoca de Muizon 1981BDR85, D07 | `--A. longirostris de Muizon 1981BDR85 `--Hydrurga Gistel 1848FS15, C57 [incl. Ogmorhinus Peters 1875C57, Stenorhynchotes Turner 1888C57] `--*H. leptonyx (Blainville 1820) (see below for synonymy)C57 Inorganic: Mirounga leconina minilorientalis Okamura 1987O87 Monachus schauinslandi protominilorientalus Okamura 1987O87
*Hydrurga leptonyx (Blainville 1820) [=Phoca leptonyx, Ogmorhinus leptonyx, Ogmorhynus leptonyx, Stenorhincus leptonyx, Stenorhynchus leptonyx; incl. Phoca homei Lesson 1828]C57
*Leptonychotes weddellii (Lesson 1826) [=Otaria weddellii, Leptonix weddelii, Leptonyx weddellii, Phoca weddelii, Phoca weddellii, Poecilophoca weddelli, Stenorhynchus weddellii; incl. Phoca leopardina Hamilton Smith 1839, Leptonyx leopardinus]C57
*Lobodon carcinophagus (Jacquinot & Pucheran 1842) [=Phoca carcinophaga, L. carcinophaga, Ogmorhinus carcinophagus, Stenorhynchus carcinophagus; incl. S. serridens Owen 1843]C57
Mirounga Gray in Griffith 1827FS15, C57 [=Morunga Gray 1843C57; incl. Macrorhinus Cuvier 1826 non Latreille 1825C57, Macrorhyna (l. c.)C57, Physorhinus Gloger 1841 non Germar 1840C57, Rhinophoca Wagler 1830C57; Miroungini]
Mirounga leonina (Linnaeus 1758) [=Phoca leonina, Macrorhinus leoninus; incl. P. ansonii Desmarest 1820, Ma. ansonii, Mirounga ansonii, Phoca coxii Desmarest 1820, Macrorhinus coxii, Ma. leoninus crosetensis Lydekker 1909, Phoca dubia Fischer 1829, P. elephantina Molina 1782, Cystophora elephantina, Macrorhinus elefantinus, Morunga elephantina, Cystophora falklandica Peters 1875, Macrorhinus leoninus flaclandicus, C. kerguelensis Peters 1875, Ma. leoninus macquariensis Lydekker 1909, Mirounga patagonica Gray 1827, Phoca proboscidea Péron 1817, Cystophora proboscidea, Macrorhinus proboscideus, *Mirounga proboscidea, Phoca resima Péron 1817, Macrorhinus leoninus typicus Lydekker 1909]C57
*Type species of generic name indicated
References
[AG06] Arnason, U., A. Gullberg, A. Janke, M. Kullberg, N. Lehman, E. A. Petrov & R. Väinölä. 2006. Pinniped phylogeny and a new hypothesis for their origin and dispersal. Molecular Phylogenetics and Evolution 41 (2): 345–354.
[BDR85] Barnes, L. G., D. P. Domning & C. E. Ray. 1985. Status of studies on fossil marine mammals. Marine Mammal Science 1 (1): 15–53.
[BR05] Bouchet, P., & J.-P. Rocroi. 2005. Classification and nomenclator of gastropod families. Malacologia 47 (1–2): 1–397.
[C57] Cabrera, A. 1957. Catalogo de los mamiferos de America del Sur. I (Metatheria—Unguiculata—Carnivora). Revista del Museo Argentino de Ciencias Naturales “Bernardino Rivadavia” e Instituto Nacional de Investigacion de Las Ciencias Naturales, Ciencias Zoológicas 4 (1): 1–307.
Davis, C. S., I. Delisle, I. Stirling, D. B. Siniff & C. Strobeck. 2004. A phylogeny of the extant Phocidae inferred from complete mitochondrial DNA coding regions. Molecular Phylogenetics and Evolution 33 (2): 363–377.
[D07] Dixon, D. 2007. The Complete Illustrated Encyclopedia of Dinosaurs & Prehistoric Creatures. Hermes House: London.
[FS15] Faurby, S., & J.-C. Svenning. 2015. A species-level phylogeny of all extant and late Quaternary extinct mammals using a novel heuristic-hierarchical Bayesian approach. Molecular Phylogenetics and Evolution 84: 14–26.
[G76] Grigorescu, D. 1976. Paratethyan seals. Systematic Zoology 25 (4): 407–419.
Harcourt, R. G. 2001. Advances in New Zealand mammalogy 1990–2000: pinnipeds. Journal of the Royal Society of New Zealand 31 (1): 135–160.
[O87] Okamura, C. 1987. New facts: Homo and all Vertebrata were born simultaneously in the former Paleozoic in Japan. Original Report of the Okamura Fossil Laboratory 15: 347–573.
[R76] Ray, C. E. 1976. Geography of phocid evolution. Systematic Zoology 25 (4): 391–406.
[SM93] Stucky, R. K., & M. C. McKenna. 1993. Mammalia. In: Benton, M. J. (ed.) The Fossil Record 2 pp. 739–771. Chapman & Hall: London.
[T76] Tedford, R. H. 1976. Relationship of pinnipeds to other carnivores (Mammalia). Systematic Zoology 25 (4): 363–374.
Walsh, S., & D. Naish. 2002. Fossil seals from Late Neogene deposits in South America: a new pinniped (Carnivora, Mammalia) assemblage from China. Palaeontology 45 (4): 821–842.
Surely "Aquatic" is plesiomorphic?
Well, Tedford was one of those who supported a diphyletic Pinnipedia. I think a homodont dentition might also be characteristic of Pinnipedia as a whole, not just phocids.
I could also try and weasel out of it by saying that I'd referred to 'synapomorphies', not 'autapomorphies' :-P