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Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal.

Gheerbrant E, Amaghzaz M, Bouya B, Goussard F, Letenneur C - PLoS ONE (2014)

Bottom Line: This results from conflict with undetected convergences of Paenungulata and Perissodactyla in our cladistic analysis, such as the shared bilophodonty.The selenodont pattern best supports the stem paenungulate position of Ocepeia; that, however, needs further support.In addition, the autapomorphic family Ocepeiidae supports the old--earliest Tertiary or Cretaceous--endemic evolution of placentals in Africa, in contrast to hypotheses rooting afrotherians in Paleogene Laurasian "condylarths".

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, CNRS-MNHN-UPMC, Muséum National d'Histoire Naturelle, Dpnt Histoire de la Terre, Paris, France.

ABSTRACT
While key early(iest) fossils were recently discovered for several crown afrotherian mammal orders, basal afrotherians, e.g., early Cenozoic species that comprise sister taxa to Paenungulata, Afroinsectiphilia or Afrotheria, are nearly unknown, especially in Africa. Possible stem condylarth-like relatives of the Paenungulata (hyraxes, sea-cows, elephants) include only Abdounodus hamdii and Ocepeia daouiensis from the Selandian of Ouled Abdoun Basin, Morocco, both previously only documented by lower teeth. Here, we describe new fossils of Ocepeia, including O.grandis n. sp., and a sub-complete skull of O. daouiensis, the first known before the Eocene for African placentals. O.daouiensis skull displays a remarkable mosaic of autapomophic, ungulate-like and generalized eutherian-like characters. Autapomorphies include striking anthropoid-like characters of the rostrum and dentition. Besides having a basically eutherian-like skull construction, Ocepeia daouiensis is characterized by ungulate-like, and especially paenungulate-like characters of skull and dentition (e.g., selenodonty). However, some plesiomorphies such as absence of hypocone exclude Ocepeia from crown Paenungulata. Such a combination of plesiomorphic and derived characters best fits with a stem position of Ocepeia relative to Paenungulata. In our cladistic analyses Ocepeia is included in Afrotheria, but its shared derived characters with paenungulates are not optimized as exclusive synapomorphies. Rather, within Afrotheria Ocepeia is reconstructed as more closely related to insectivore-like afroinsectiphilians (i.e., aardvarks, sengis, tenrecs, and golden moles) than to paenungulates. This results from conflict with undetected convergences of Paenungulata and Perissodactyla in our cladistic analysis, such as the shared bilophodonty. The selenodont pattern best supports the stem paenungulate position of Ocepeia; that, however, needs further support. The remarkable character mosaic of Ocepeia makes it the first known "transitional fossil" between insectivore-like and ungulate-like afrotherians. In addition, the autapomorphic family Ocepeiidae supports the old--earliest Tertiary or Cretaceous--endemic evolution of placentals in Africa, in contrast to hypotheses rooting afrotherians in Paleogene Laurasian "condylarths".

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Relationships of Ocepeia.Cladogram resulting from parsimony analysis with TNT version 1.1 program of modified matrix of Gheerbrant [68] (Text S1, parts I-II). 152 features are processed as ordered in contrast to Figure 21 (Text S1, part I). Strict consensus of 2 trees resulting from the “traditional search” command (Text S1, part III, Cladogram 3). Tree lengths: 665. Retention index: 54.6. Consistency Index: 37. In Figure 22b, the black and open white circles represent respectively strict and homoplasic synapomorphies. This is our reference topology for our discussion of the relationships of Ocepeia. In this analysis Ocepeia is also strongly autapomorphic.
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pone-0089739-g022: Relationships of Ocepeia.Cladogram resulting from parsimony analysis with TNT version 1.1 program of modified matrix of Gheerbrant [68] (Text S1, parts I-II). 152 features are processed as ordered in contrast to Figure 21 (Text S1, part I). Strict consensus of 2 trees resulting from the “traditional search” command (Text S1, part III, Cladogram 3). Tree lengths: 665. Retention index: 54.6. Consistency Index: 37. In Figure 22b, the black and open white circles represent respectively strict and homoplasic synapomorphies. This is our reference topology for our discussion of the relationships of Ocepeia. In this analysis Ocepeia is also strongly autapomorphic.

Mentions: Embrithopoda. A clade (Minchenella (Phenacolophus (Embrithopoda))) is very stable (several analyses, see Text S1). It is supported by 10 homoplastic features in the ordered analysis (Fig. 22). However, it should be noted that a recent analysis of dental enamel microstructure argues against close relationships of Phenacolophus and Embrithopoda [77]. We concur, and suggest that the cladistic relationships of Phenacolophus recovered here results from unresolved significant dental convergences, in the same way as between perissodactyls and paenungulates. This is probably related to our poor knowledge of Phenacolophus (59% of its characters unknown in matrix) and Minchenella (50% of its characters unknown in matrix) which are known only by dental specimens and are among the less known analysed taxa. Actually, it should be emphasized that even the described dental material of Phenacolophus[78] is very poorly preserved – a point which is widely underestimated in current phylogenetic discussions; for instance the structural dental homology remains widely to check. Embrithopods are usually sister-group of Sirenia as recovered by Seiffert [73], except in partitioned analysis (ordered) restricted to dental traits in which they are stem tethytheres (Text S1, part III, Cladograms 5-6).


Ocepeia (Middle Paleocene of Morocco): the oldest skull of an afrotherian mammal.

Gheerbrant E, Amaghzaz M, Bouya B, Goussard F, Letenneur C - PLoS ONE (2014)

Relationships of Ocepeia.Cladogram resulting from parsimony analysis with TNT version 1.1 program of modified matrix of Gheerbrant [68] (Text S1, parts I-II). 152 features are processed as ordered in contrast to Figure 21 (Text S1, part I). Strict consensus of 2 trees resulting from the “traditional search” command (Text S1, part III, Cladogram 3). Tree lengths: 665. Retention index: 54.6. Consistency Index: 37. In Figure 22b, the black and open white circles represent respectively strict and homoplasic synapomorphies. This is our reference topology for our discussion of the relationships of Ocepeia. In this analysis Ocepeia is also strongly autapomorphic.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3935939&req=5

pone-0089739-g022: Relationships of Ocepeia.Cladogram resulting from parsimony analysis with TNT version 1.1 program of modified matrix of Gheerbrant [68] (Text S1, parts I-II). 152 features are processed as ordered in contrast to Figure 21 (Text S1, part I). Strict consensus of 2 trees resulting from the “traditional search” command (Text S1, part III, Cladogram 3). Tree lengths: 665. Retention index: 54.6. Consistency Index: 37. In Figure 22b, the black and open white circles represent respectively strict and homoplasic synapomorphies. This is our reference topology for our discussion of the relationships of Ocepeia. In this analysis Ocepeia is also strongly autapomorphic.
Mentions: Embrithopoda. A clade (Minchenella (Phenacolophus (Embrithopoda))) is very stable (several analyses, see Text S1). It is supported by 10 homoplastic features in the ordered analysis (Fig. 22). However, it should be noted that a recent analysis of dental enamel microstructure argues against close relationships of Phenacolophus and Embrithopoda [77]. We concur, and suggest that the cladistic relationships of Phenacolophus recovered here results from unresolved significant dental convergences, in the same way as between perissodactyls and paenungulates. This is probably related to our poor knowledge of Phenacolophus (59% of its characters unknown in matrix) and Minchenella (50% of its characters unknown in matrix) which are known only by dental specimens and are among the less known analysed taxa. Actually, it should be emphasized that even the described dental material of Phenacolophus[78] is very poorly preserved – a point which is widely underestimated in current phylogenetic discussions; for instance the structural dental homology remains widely to check. Embrithopods are usually sister-group of Sirenia as recovered by Seiffert [73], except in partitioned analysis (ordered) restricted to dental traits in which they are stem tethytheres (Text S1, part III, Cladograms 5-6).

Bottom Line: This results from conflict with undetected convergences of Paenungulata and Perissodactyla in our cladistic analysis, such as the shared bilophodonty.The selenodont pattern best supports the stem paenungulate position of Ocepeia; that, however, needs further support.In addition, the autapomorphic family Ocepeiidae supports the old--earliest Tertiary or Cretaceous--endemic evolution of placentals in Africa, in contrast to hypotheses rooting afrotherians in Paleogene Laurasian "condylarths".

View Article: PubMed Central - PubMed

Affiliation: Centre de Recherches sur la Paléobiodiversité et les Paléoenvironnements, CNRS-MNHN-UPMC, Muséum National d'Histoire Naturelle, Dpnt Histoire de la Terre, Paris, France.

ABSTRACT
While key early(iest) fossils were recently discovered for several crown afrotherian mammal orders, basal afrotherians, e.g., early Cenozoic species that comprise sister taxa to Paenungulata, Afroinsectiphilia or Afrotheria, are nearly unknown, especially in Africa. Possible stem condylarth-like relatives of the Paenungulata (hyraxes, sea-cows, elephants) include only Abdounodus hamdii and Ocepeia daouiensis from the Selandian of Ouled Abdoun Basin, Morocco, both previously only documented by lower teeth. Here, we describe new fossils of Ocepeia, including O.grandis n. sp., and a sub-complete skull of O. daouiensis, the first known before the Eocene for African placentals. O.daouiensis skull displays a remarkable mosaic of autapomophic, ungulate-like and generalized eutherian-like characters. Autapomorphies include striking anthropoid-like characters of the rostrum and dentition. Besides having a basically eutherian-like skull construction, Ocepeia daouiensis is characterized by ungulate-like, and especially paenungulate-like characters of skull and dentition (e.g., selenodonty). However, some plesiomorphies such as absence of hypocone exclude Ocepeia from crown Paenungulata. Such a combination of plesiomorphic and derived characters best fits with a stem position of Ocepeia relative to Paenungulata. In our cladistic analyses Ocepeia is included in Afrotheria, but its shared derived characters with paenungulates are not optimized as exclusive synapomorphies. Rather, within Afrotheria Ocepeia is reconstructed as more closely related to insectivore-like afroinsectiphilians (i.e., aardvarks, sengis, tenrecs, and golden moles) than to paenungulates. This results from conflict with undetected convergences of Paenungulata and Perissodactyla in our cladistic analysis, such as the shared bilophodonty. The selenodont pattern best supports the stem paenungulate position of Ocepeia; that, however, needs further support. The remarkable character mosaic of Ocepeia makes it the first known "transitional fossil" between insectivore-like and ungulate-like afrotherians. In addition, the autapomorphic family Ocepeiidae supports the old--earliest Tertiary or Cretaceous--endemic evolution of placentals in Africa, in contrast to hypotheses rooting afrotherians in Paleogene Laurasian "condylarths".

Show MeSH
Related in: MedlinePlus