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Diedrich, Cajus G.
(detail)
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2008 |
The food of the miosiren Anomotherium langenwieschei [sic] (Siegfried) - indirect proof of seaweed or seagrass by xenomorphic oyster fixation structures in the Upper Oligocene (Neogene [sic]) of the Doberg, Bünde (NW Germany) and comparisons to modern Dugong dugon (Müller) feeding strategies.
Senckenbergiana Maritima 38(1): 59-73. 12 figs. May 9, 2008.
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Diedrich, Cajus G.
(detail)
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2010 |
Palaeoecology of Placodus gigas (Reptilia) and other placodontids - Middle Triassic macroalgae feeders in the Germanic Basin of central Europe - and evidence for convergent evolution with Sirenia.
Palaeogeogr. Palaeoclim. Palaeoecol. 285(3-4): 287-306. 18 figs. Jan. 15, 2010 (available online Nov. 24, 2009).
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Diedrich, Cajus G.
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2011 |
Fossil Middle Triassic "sea cows" - placodont reptiles as macroalgae feeders along the north-western Tethys coastline with Pangaea and in the Germanic Basin.
Natural Science 3(1): 9-27. 11 figs. DOI: :10.4236/ns.2011.31002. Jan. 2011.
–ABSTRACT: The descriptions of fossil Triassic marine placodonts as durophagous reptiles are revised through comparisons with the sirenia and basal proboscidean mammal and palaeoenvironment analyses. The jaws of placodonts are convergent with those of Halitherium/Dugong or Moeritherium in their general function. Whereas Halitherium possessed a horny oral pad and counterpart and a special rasp-like tongue to grind seagrass, as does the modern Dugong, placodonts had large teeth that covered their jaws to form a similar grinding pad. The Sirenia also lost their anterior teeth during many millions of years and built a horny pad instead and specialized tongue to fed mainly on seagrass, whereas placodonts had only macroalgae available. Indirect evidence for Triassic macroalgae is provided by benthic palaeocommunities from different layers and extended European regions in the Germanic Basin. Studies of tooth wear stages for Placodus indicate that anterior teeth may have been used in a similar manner to the procumbent front teeth of modern Dugong. Paraplacodus and Placodus seem to have used these teeth as spatulas to dig out seaplants. Cyamodus and other placodonts such as Placochelys had smaller or reduced anterior teeth. The scarcity of highly worn palatine or maxillary and lower jaw dentary Placodus or Cyamodus teeth (less then 0.5%) suggests that they had a relatively soft diet. The seaplants would only have been squeezed in a similar feeding strategy to that of modern Dugong feeding on seagrass without jaw rotation and grinding. The phylogenetic trend in tooth reduction within the placodonts Paraplacodus, Placodus, especially in Cyamodus but also Placochelys, and Henodus within 11 My appears to have been a result of this plant-feeding adaptation and may even explain the origin or at least close relationship of the earliest Upper Triassic turtles as toothless algae and jellyfish feeders, in terms of the long-term convergent development with the sirens.
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Diedrich, Cajus G.
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2013a |
The most northerly record of the sirenian Protosiren and the possible polyphyletic evolution of manatees and dugongs.
Natural Science 5(11): 1154-1164. 4 figs. DOI: 10.4236/ns.2013.511142 Nov. 4, 2013.
–ABSTRACT: Newly discovered remains of the early Middle Eocene (Lutetian) sirenian Protosiren (Protosirenidae) in shark tooth rich conglomerates from a coastal delta environment northwest of the European Rhenish Massif at Fürstenau (northwestern Germany), represent the most northerly occurrence of this genus whose global distribution was generally restricted to warm waters. Its presence of the remains so far north can be explained by seasonal inflow of warm Tethys surface water into the cool, upwelling-influenced, basin. The existence of two discrete centers of sirenian evolution can be explained by the opening of the Atlantic and the upwelling that separated the North American warm water faunal province from those of Africa and Eurasia. A slightly modified evolutionary model is presented in which the oldest Early Eocene manatee sirenians evolved in the Caribbean of Central America. Protosiren, however, appears to have developed polyphyletically along the African coastline of the Tethys, and represents the oldest known dugong ancestor. Younger (Oligocene) European sirenian skeletons of Halitherium and Anomotherium are included in the phylostratigraphic model in which sirenians had generally reduced their teeth by 28 Ma as an adaptation for feeding on sea-plants (macroalgae/seagrass). Teeth from early megatooth sharks, which preyed on sirenians, have been recorded from shallow marine Eocene and Oligocene coastlines of the southern proto-North Sea Basin, and shark bite marks have been found on sirenian skeletons.
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Diedrich, Cajus G.
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2013b |
Evolution of white and megatooth sharks, and evidence for early predation on seals, sirenians, and whales.
Natural Science 5(11): 1203-1218. 6 figs. DOI: 10.4236/ns.2013.511148 Nov. 13, 2013.
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Bibliography and Index of the Sirenia and Desmostylia 