Access

You are not currently logged in.

Access your personal account or get JSTOR access through your library or other institution:

login

Log in to your personal account or through your institution.

If You Use a Screen Reader

This content is available through Read Online (Free) program, which relies on page scans. Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.

Diets, Habitat Preferences, and Niche Differentiation of Cenozoic Sirenians from Florida: Evidence from Stable Isotopes

Bruce J. MacFadden, Pennilyn Higgins, Mark T. Clementz and Douglas S. Jones
Paleobiology
Vol. 30, No. 2 (Spring, 2004), pp. 297-324
Published by: Paleontological Society
Stable URL: http://www.jstor.org/stable/4096848
Page Count: 28
  • Read Online (Free)
  • Download ($12.00)
  • Subscribe ($19.50)
  • Cite this Item
Since scans are not currently available to screen readers, please contact JSTOR User Support for access. We'll provide a PDF copy for your screen reader.
Diets, Habitat Preferences, and Niche Differentiation of Cenozoic Sirenians from Florida: Evidence from Stable Isotopes
Preview not available

Abstract

Cenozoic sediments of Florida contain one of the most highly fossiliferous sequences of extinct sirenians in the world. Sirenians first occur in Florida during the Eocene (ca. 40 Ma), have their peak diversity during the late Oligocene-Miocene (including the widespread dugongid Metaxytherium), and become virtually extinct by the late Miocene (ca. 8 Ma). Thereafter during the Pliocene and Pleistocene, sirenians are represented in Florida by abundant remains of fossil manatees (Trichechus sp.). Stable isotopic analyses were performed on 100 teeth of fossil sirenians and extant Trichechus manatus from Florida in order to reconstruct diets (as determined from δ13C values) and habitat preferences (as determined from δ18O values) and test previous hypotheses based on morphological characters and associated floral and faunal remains. A small sample (n = 6) of extant Dugong dugon from Australia was also analyzed as an extant model to interpret the ecology of fossil dugongs. A pilot study of captive manatees and their known diet revealed an isotopic enrichment $(\varepsilon^{*})$ in δ13C of $14.0\textperthousand$, indistinguishable from previously reported ε* for extant medium to large terrestrial mammalian herbivores with known diets. The variation in $\delta^{18}8O_{V-SMOW}$ reported here is interpreted to indicate habitat preferences, with depleted tooth enamel values $(\approx 25\textperthousand)$ representing freshwater rivers and springs, whereas enriched values $(\approx 30\textperthousand)$ indicate coastal marine environments. Taken together, the Eocene to late Miocene sirenians (Protosirenidae and Dugongidae) differ significantly in both δ13C and δ18O from Pleistocene and Recent manatees (Trichechidae). In general, Protosiren and the fossil dugongs from Florida have carbon isotopic values that are relatively positive $(mean \delta^{13}C = -0.9\textperthousand)$ ranging from $-4.8\textperthousand$ to $5.6\textperthousand$, interpreted to represent a specialized diet of predominantly seagrasses. The oxygen isotopic values $(mean \delta^{18}O = 29.2\textperthousand)$ are likewise relatively positive, indicating a principally marine habitat preference. These interpretations correlate well with previous hypotheses based on morphology (e.g., degree of rostral deflection) and the known ecology of modern Dugong dugon from the Pacific Ocean. In contrast, the fossil and extant Trichechus teeth from Florida have relatively lower carbon isotopic values $(mean \delta^{13}C = -7.2\textperthousand)$ that range from $-18.2\textperthousand$ to $1.7\textperthousand$, interpreted as a more generalized diet ranging from C3 plants to seagrasses. The relatively lower oxygen isotopic values $(mean \delta^{18}O = 28.1\textperthousand)$ are interpreted as a more diverse array of freshwater and marine habitat preferences than that of Protosiren and fossil dugongs. This study of Cenozoic sirenians from Florida further demonstrates that stable isotopes can test hypotheses previously based on morphology and associated floral and faunal remains. All these data sets taken together result in a more insightful approach to reconstructing the paleobiology of this interesting group of ancient aquatic mammalian herbivores.

Page Thumbnails

  • Thumbnail: Page 
[297]
    [297]
  • Thumbnail: Page 
298
    298
  • Thumbnail: Page 
299
    299
  • Thumbnail: Page 
300
    300
  • Thumbnail: Page 
301
    301
  • Thumbnail: Page 
302
    302
  • Thumbnail: Page 
303
    303
  • Thumbnail: Page 
304
    304
  • Thumbnail: Page 
305
    305
  • Thumbnail: Page 
306
    306
  • Thumbnail: Page 
307
    307
  • Thumbnail: Page 
308
    308
  • Thumbnail: Page 
309
    309
  • Thumbnail: Page 
310
    310
  • Thumbnail: Page 
311
    311
  • Thumbnail: Page 
312
    312
  • Thumbnail: Page 
313
    313
  • Thumbnail: Page 
314
    314
  • Thumbnail: Page 
315
    315
  • Thumbnail: Page 
316
    316
  • Thumbnail: Page 
317
    317
  • Thumbnail: Page 
318
    318
  • Thumbnail: Page 
319
    319
  • Thumbnail: Page 
320
    320
  • Thumbnail: Page 
321
    321
  • Thumbnail: Page 
322
    322
  • Thumbnail: Page 
323
    323
  • Thumbnail: Page 
324
    324