-Quantifying a Possible Miocene Phyletic Change in Hemipristis (Chondrichthyes) Teeth (study revealing how Hemipristis spp. Teeth changed over time): http://palaeo-electronica.org/2006_1/teeth/teeth.pdf
-Sirenians, seagrasses, and Cenozoic ecological change in the Caribbean D.P. Domning: http://foodweb.uhh.hawaii.edu/mare390_files/domning%202001.pdf
Notes: Rich fossil history of Sirenians in the Caribbean
Eocene: Amphibious ancestors, seagrass fossils from late middle Eocene North FL (so def. intimately tied to feeding on them, nutritious rhizomes, but also eat seagrass leaves)
Oligocene: Dugongids in early to late Olig, Metaxytherium in Latest olig/ earliest Mio;
Miocene: (earliest known true manatee from mid mio, Columbia, still only in south America/ freshwater/ maybe slightly estuarine) “In the Caribbean it apparently gave rise, with little change, to M. Floridanum, which died out by the end of the Miocene (although other species of the genus survived into the Late Pliocene in the Mediterranean Sea; Domning and Thomas, 1987). The near-absence of morphological change in Metaxytherium from the Late Oligocene to the Late Miocene is the only known example of prolonged evolutionary stasis in the entire fossil record of the Sirenia” (genus in early Miocene Caribbean & east pacific)
(Interesting: “A slight increase in body size and rostral deflection (though not tusk size) seen in the transition from M. crataegense to M. floridanum (Fig. 1) suggests some change in feeding ecology, possibly a broadening of the niche in response to the extinction of Crenatosiren and/or some other taxon..”) Seems M. floridanum couldn’t go too shallow bc of large size (states later dugongids were smaller, may have allowed them access to smaller spots M. floridanum couldn’t access)
Pliocene: Manatees expanded to north america, Last known dugong from West Atlantic (from Caloosahatchee Formation) related to modern dugongs
Pleist: Early pleist manatee fossils from Leisey
Miocene Marine extinctions
“This joint extinction of seagrasses and the sirenians that depended on them would in turn apparently have coincided with, and could easily have resulted from, the cooling and other paleoceanographic changes in the Caribbean around that time, as noted by Ivany et al. (1990). In particular, decline in upwelling and other changes in circulation patterns, resulting in reduced biological productivity, could have been important (Petuch, 1982; Jones and Hasson, 1985; Allmon et al., 1996). The Pliocene closure of the Central American Seaway (complete by ca. 3.1 Ma) coincided with signi®cant environmental and faunal changes in the Caribbean as well as the eastern Pacific (Jackson et al., 1996); in particular, there was an extinction of shallow-water molluscs in the Caribbean and West Atlantic, apparently correlated with changes in salinity and circulation patterns (Vermeij, 1978; Stanley and Campbell, 1981; Keigwin, 1982; Petuch, 1982; Jones and Hasson, 1985; Duque-Caro, 1990). Allmon et al. (1996) also point out Late Pliocene changes in assemblages of calcareous algae and plankton, as well as regional extinctions among turritellid gastropods, seabirds, cetaceans, and pinnipeds, and extinction of the giant shark Carcharodon megalodon. Budd et al. (1996) estimated that 75% of the Early to early Late Pliocene reef coral species became extinct in the Caribbean. It is therefore plausible that this major upheaval in Caribbean marine ecology also made itself felt among seagrasses and sirenians. In fact, the corals most affected by this turnover were precisely those associated with seagrasses, which showed extinction rates of 30±50% per million years (Budd et al., 1996). Likewise, seagrass associated bryozoans (Metrarabdotos spp.) underwent dramatic extinction in the latest Miocene and the Pliocene (Cheetham and Jackson, 1996). Both these trends are interpreted by the respective authors as indicating decline of the seagrasses themselves.” (seems manatees might have outcompeted dugongs, but seems much more plausible they died out due to environmental causes and manatees/ some other dugongs (briefly) swooped in)
+1 more excerpt concerning last dugongid in Atlantic during Late Pliocene, see Manatee/dugong evolution page.
-The Pliocene marine megafauna extinction and its impact on functional diversity
Possibly new species of Hemipristis (2011, only found the species name while searching a database of fish names) https://www.researchgate.net/publication/269163945_MIOCENE_PALAEOBIOLOGY_OF_MIZORAM_PRESENT_STATUS_AND_FUTURE_PROSPECT