Steller's Sea Cow: Hydrodamalis gigas

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Two other common names for Steller's sea cow are the German "Borkentier," referring to its rough bark-like hide, and the Russian "kapustnik" (cabbage eater), which Steller attributed to inhabitants of Kamchatka, where dead sea cows reportedly washed ashore after storms. There is no evidence for geographic variation. The northernmost Pacific was likely a marginal habitat as members of the Kommandorskiye population may have been stunted. Adults at Bering Island had a body length approximately 750 cm (25 ft) and a weight of 4500-5900 kg. Fossil material from farther south suggests maximum body lengths may have reached 9-10 m. Like other sirenians, Steller's sea cow had paired nostrils, abdominal testes, a pair of axillary mammae, no hindlimbs, horny plates on the occlusal surfaces of the rostrum and mandibular symphysis for macerating vegetation, and ribs and other bones that were swollen and completely compact. Historically, Steller's sea cow was known only from Bering and Medney (Copper) Islands at the western terminus of the Aleutians, 200 miles to the west of Attu Island and 150 miles east of the Kamchatka Peninsula. Mating apparently involved only a pair, with the male following or herding the female during prolonged "amorous preludes." Copulation involved mutual clasping with the pectorals, the female in an inverted position and the male above. These magnificent animals would have been at least as vulnerable to healthy and skilled Pleistocene hunters along mainland shores. Steller's sea cows had no fear of humans. Feeding with the head submerged and half of the back above water they were easily approached and could be touched or speared from the rocks. Decimation of the otters in all probability triggered a sea urchin population explosion and the disappearance of chemically undefended shallow water kelps that were the sea cows' main food supply. Invasion of the shallow waters by chemically defended deep-water kelps left the hunted remnant of the sea cow population with kelp that was likely toxic.

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... Dess maximala vikt är okänd men enligt Steller (1751) krävdes de sammanslagna krafterna av 30 män för att släpa en harpunerad hona i land (se även Scheffer 1972). Längden på detta exemplar var ungefär 7,5 meter, men vissa individer kunde uppenbarligen bli ännu större, sannolikt upp till 10 meter långa (Anderson & Domning 2008). Näst efter de stora valarna bör Stellers sjöko ha varit ett av de största däggdjur som någonsin funnits. ...
... Utrymmet tillåter inte en detaljerad översikt av de talrika undersökningar av och översiktsarbeten om Stellers sjöko som gjorts ända sedan början av 1800-talet. Viktiga publikationer från olika tidsperioder, förutom de redan citerade källorna, inkluderar dock Brandt (1833Brandt ( , 1849Brandt ( , 1868Brandt ( , 1871, von Baer (1840), Stejneger (1887), Büchner (1891), Simpson (1932), Kleinschmidt (1951), von Haffner (1957, Mohr (1957), Heptner (1966, 1974, 1998), Chelnokov (1969, Domning (1976Domning ( , 1978, Anderson (1995), Lysén (2005), Turvey & Risley (2006), Anderson & Domning (2008), Rothauscher (2008) och Estes et al. (2016). Det kan tilläggas att man också har lyckats utvinna DNA ur rester av Stellers sjöko. ...
Analysis of 62 cranial and dental characters of 36 species and subspecies of sirenians, by means of the Hennig86 computer program without character weighting, produced 60 maximally parsimonious trees (length 152, consistency index 0.55, retention index 0.83). With successive character weighting, these were reduced to six maximally parsimonious trees, of which the Nelson consensus tree is presented here (length 162, consistency index 0.76, retention index 0.91). Sample size and intrapopulated variation are insufficiently studied problems in cladistic analysis and a statistically based method for scoring variable characters is introduced. The tree's topology is least certain in three groups of taxa: Eocene dugongids, dugongines (here including rytiodontines), and species of Metaxytherium. -from Author