Here we describe 31 fossil teeth, deposited in the paleontological collections of the Museo di Storia Naturale di Milano (MSNM), that come from the inland portion of the Mahajanga Basin, NW Madagascar, namely from the Sakahara Formation (classically known as Isalo IIIb subunit), which is dated back to the Middle Jurassic Bathonian stage. Based on detailed morphological characters, the eight morphotypes recognised herein are tentatively referred to four sauropod taxa: Archaeodontosaurus descouensi, ‘Bothriospondylus madagascariensis’, Lapparentosaurus madagascariensis, and an indeterminate specialised eusauropod, which may represent a new species, and the first evidence of a Bathonian diplodocoid in Madagascar.
The identification of the teeth is corroborated by comparative examination of morphometric data. In this paper we provide evidence that Titanosauriformes were present in the Bathonian, on the basis of seven specimens referable to this clade. We also discuss in detail some dental characters that support the existence of a clear niche partitioning between the above mentioned taxa, that co–existed in the Malagasy Middle Jurassic terrestrial ecosystem. We finally hypothesise, for the first time, a direct correlation between the pattern drawn on the tooth crown by the enamel wrinkles and the feeding ecology of sauropod dinosaurs. The enamel wrinkles likely played a structural function: coarse wrinkles were associated to a diet composed mainly by hard foodstuff, whereas fainter wrinkles, which appeared in more derived morphologies, were associated to a diet composed by softer foodstuff.
S1 - 3D model of MSNM V5801
Specimen MSNM V5801 comes from the Sakaraha Formation (Isalo IIIb subunit), which is Bathonian in age (Middle Jurassic). It has been collected in 2001, in association with MSNM V5802 and V5803, near the Tsinjorano village school (Majunga Province, NW Madagascar). It was lying near two theropod teeth and two fragmentary sauropod long bones, almost completely powdered by weathering (G. Pasini, pers. com. 2016). This specimen is attributed to morphotype J2 and included in taxon A, which represents a taxon more derived than Mamenchisauridae but not belonging to Titanosauriformes and Diplodocoidea.
This 3D model has been generated with photogrammetry processing and merging 34 photos together; an object with about 180000 faces has been obtained.
Description in the main text.
3D model of MSNM V5801.pdf
S2 - 3D model of MSNM V6216
Specimen MSNM V6216 comes from the Sakaraha Formation (Isalo IIIb subunit), which is Bathonian in age (Middle Jurassic). It has been collected in 2003, isolated from other fossils. A peculiar character of this specimen is the twisting of the crown, where it approaches the crown tip. This character has been considered to be a synapomorphy of Brachiosauridae (D’Emic 2012). It is attributed to morphotype J3 and included in taxon B, which represents a basal Brachiosauridae or basal Titanosauriformes.
This 3D model has been generated with photogrammetry processing and merging 71 photos together, divided in two groups, to obtain an object with about 795000 faces.
Description in the main text.
3D model of MSNM V6216.pdf
S3 - 3D model of MSNM V6217
Specimen MSNM V6217 comes from the Sakaraha Formation (Isalo IIIb subunit), which is Bathonian in age (Middle Jurassic). It has been collected in 2003, isolated from other fossils. It is distinguished by a unique elongate, spindle–like shape, and by a transverse section that remains subcircular up to one-third of the crown height. This specimen is the only representative of morphotype J8, taxon D, which should belong to Diplodocoidea (Dicraeosauridae?) or Titanosauria. MSNM V6217 might represent a new taxon, maybe a basal member of Diplodocoidea, and the oldest fossil record of the clade in Africa.
This 3D model has been generated with photogrammetry processing and merging 50 photos together, divided in two groups, to obtain an object with about 1000000 faces.
Description in the main text.
3D model of MSNM V6217.pdf