Scientific Illustration

animal-anatomy:

Anatomy of Sirenian from http://www.xavier.edu/manateeresearch/Anatomy-and-Physiology.cfm

Sirenians: dugong and manatee

Dugong feeding behaviour

(A) Upon approaching the vegetation the oral disk is flared. This involves contraction of the snout along its entire length, pulling the orofacial ridge dorsally and laterally. Simultaneously, the pair of lateral furrows open and expand, resulting in the extension of the lateral flaps and a shape change of the oral disk from arched and convex to semicircular and flat.

(B) Perioral bristle movement (U1 and U2) begins near the midline, adjacent to the central crease. The upper lip (ventral margin of the oral disk) is lifted slightly to either side of the central crease of the oral disk to form a small, characteristic ‘M’ shape. The lip margin, where the U1 bristle fields are located, curls rostrally.

(C) Both U2 bristle fields are maximally everted rostrally near the midline, and each field begins to move laterally. Simultaneously, the raised peaks of the upper lip travel laterally in a wave-like action. At this time the lower jaw begins to open.

(D) At the ventrolateral corner of the oral disk the U2 bristle fields change directions and move caudally. During these events, the lower jaw continues to open and reaches its maximum gape. The L1 are everted to their full extent from the fleshy lower lip pad.

(E) The U2 bristles move medially to complete a circular motion that sweeps vegetation into the side of the mouth, and then return to their original position (rostral). As the lower jaw closes, the L1 bristle fields sweep vegetation caudally into the oral cavity.

Orofacial morphology and feeding behaviour of the dugong, Amazonian, West African and Antillean manatees (Mammalia: Sirenia): functional morphology of the muscular-vibrissal complex. Christopher D. Marshall, Hiroshi Maeda, Matsumitsu Iwata, Masami Furuta, Shiro Asano, Fernando Rosas and Roger L. Reep. Journal of Zoology / Volume259 / Issue03 / March 2003, pp 245-260 DOI: http://dx.doi.org/10.1017/S0952836902003205 (About DOI), Published online: 10 March 2003 (pdf)

sireniasong:

Forelimb and hand of the manatee

Manatee and Dugong skeletons

From Recherches sur les ossemens fossiles de quadrupèdes : où l’on rétablit les caractères de plusieurs espèces d’animaux que les révolutions du globe paroissent avoir détruites Vol. 4 by Georges Cuvier, 1769-1832 

aycarambas:

Manatee from ”Historia dos animais e árvores de Maranhao”,  17th. century.

Manatee by BioDivLibrary on Flickr.

The life of animals;.
London,Macmillan & co., ltd.,1906..
biodiversitylibrary.org/page/39642125

rhamphotheca:

Lumbering Sea Cows Were Once Plentiful and Diverse

by Jennifer Welsh

Today’s sea cows are lonely: They share their habitat only with others of their species. This wasn’t always the case, new research suggests. In the past multiple species of sea cow lived together in harmony.

Sea cows, also known as Sirenians, are defined by four species, the best known in the United States being our Florida resident, the manatee. There are two other species of manatee in the Atlantic Ocean, as well as the dugong, from the Indo-Pacific.

The researchers found multiple examples of Sirenians in the same fossil bed at the same depth — evidence the two species would have lived in the same area at the same time. Before modern times, up to three species of these big herbivores (they eat mainly sea grasses) could be found together in the same area. This suggests that the environment and food sources for ancient sea cows were different in the past, but researchers weren’t sure how…

(read more: Live Science)

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(top image: Dugong, by Julien Willem)

(bttom image: Three sets of sea cows lived in three different times and locations: the late Oligocene (23 million to 28 million years ago) in Florida, the early Miocene (16 million to 23 million years ago) in India and the early Pliocene (3 million to 5 million years ago) in Mexico; illustration by Carl Buell)

rhamphotheca:

The Discovery of Multispecies Communities of Seacows

by Jorge Velez-Juarbe

Sirenians, or seacows, are a group of marine mammals that include manatees and dugongs. In the modern world, only one species of seacow is found in each world region, however, the fossil record tells a different story. According to the fossil record of these marine mammals, which dates back 50 million years ago, it was more common to find three, maybe more, different species living together at one time. This oddity hinted that seacows’ environment and food sources were different than what we see today.

Inspired by this finding, a group of paleontologists including Drs. Daryl Domning, Nick Pyenson and myself conducted research on extinct seacows from different ocean basins, in different geological times, to learn more about the paleoecology and evolution of these marine mammals.

Presently, there are only four species of living seacows. These include three species of manatees, which are found in different coastal waters of the Atlantic Ocean, and one species of dugong, found around coasts of the Indo-Pacific Ocean. All seacows are consumers of marine vegetation, and they generally concentrate on seagrasses.  The geographic distribution of living seacows shows no overlap.  However, the fossil record of seacows shows several instances where different species co-existed…

(read more: Smithsonian Ocean Portal)     (image: Carl Buell)

rhamphotheca:

biomedicalephemera: Manatus australis (now Trichecus manatus) 

West Indian Manatee

The West Indian Manatee includes the subspecies Trichecus manatus latirostris, the Florida Manatee. This is the species that likes to loll around the river heads of central-southern Florida during the winter, leading to the development of several “manatee parks” that let tourists and residents view the overwintering creatures, while also providing rehabilitation to the injured and an especially strongly protected area for the wild individuals.

Manatees belong to the order Sirenia, which also includes dugongs and the extinct Stellar’s sea cow. Unlike other marine mammals, Sirenia are primarily herbivorous, though they are opportunistic feeders and will consume small fish and crustaceans when they’re nearby.

Biologia centrali-americana: Mammalia. Edward Richard Alston, 1882.