Data for: Giant longirostrine crocodylians from the Early Miocene of Pakistan: new material and taxonomical review
Data files
May 14, 2025 version files 49.73 KB
-
README.md
3.20 KB
-
Table_1_material.xlsx
16.89 KB
-
Table_2.xlsx
13.55 KB
-
Table_3.xlsx
16.09 KB
May 14, 2025 version files 49.74 KB
-
README.md
3.20 KB
-
Table_1_material.xlsx
16.89 KB
-
Table_2.xlsx
13.55 KB
-
Table_3.xlsx
16.09 KB
Abstract
This study, based on previously undescribed crocodile remains from the Early Miocene of the Bugti Hills (Balochistan, Pakistan), reveals the existence of at least three distinct species. It confirms the validity of the species initially identified as "Gavialis" pachyrhynchus, establishing it as the sister taxon to the massive Miocene crocodile Rhamphosuchus crassidens. Consequently, it is reclassified as Rhamphosuchus pachyrhynchus. Additionally, "Gharialis" curvirostris is now acknowledged as a valid species under the new genus name Pseudogavialis, closely related to Gavialis. Another set of remains represents a third species, although the poor preservation hinders precise identification. The phylogenetic relationships between Tomistoma and Gavialis are one of the most debated issues in crocodylian phylogeny. Molecular analyses suggest a sister-taxa relationship dating back to the Early Miocene, while morphological analyses place Gavialis at the base of the tree, diverging from thoracosaurs, with a Gavialoidea/Crocodyloidea split in the Cretaceous. The inclusion of newly described species in phylogenetic analyses yields variable outcomes, highlighting the sensitivity of results to the species considered. The insertion of Portugalosuchus azenhae, found as a thoracosaurine, aligns with traditional morphological findings, while the inclusion of Indo-Pakistani species of Rhamphosuchus supports the molecular hypothesis. Nevertheless, when the molecular result is found, a large number of morphologic gavialoids and thoracosaurines make the result strongly stratigraphically incongruent. The inclusion of fossil species in the phylogenetic analyses significantly impacts the understanding of crocodylian relationships. Even when molecular results align with morphological data, the persistent stratigraphic incongruence does not resolve the Gavialis-Tomistoma dilemma.
https://doi.org/10.5061/dryad.1g1jwsv6b
Description of the data and file structure
The fossil crocodylian material of the Bugti Hills studied in this work was collected during the 1995 and 1996 expeditions of the “Mission Paléontologique Française au Baloutchistan” (MPFB). The material (more than 350 fragments, with more than 120 of mandibles, maxillae, and premaxillae) was collected from the level 0 (Rupelian, Lower Oligocene), level 4 (Aquitanian, Lower Miocene), but also from the levels 5 and 6 (Fig. 1B.; Burdigalian, Lower Miocene; Welcomme et al. 2001). The material, although fragmentary, is well preserved overall, and the studied specimens are listed in Courville et al. (2025, Table 1). The fossils are only slightly deformed, but often embedded in compact ferruginous sandstones typical of the "Bugti Bone Bed" levels (Welcomme et al. 2001).
Files and variables
Table 1. Material studied. The material is curated in the MNHN, Paris, and the IME, Calcutta. Only the material from the MNHN has been studied firsthand.
- Collection number: The museum where the specimen was stored.
- Anatomical part: Anatomical identification of the different fragments analyzed (e.g., maxilla, premaxilla, dentary, skull...).
- Identification: Taxonomic assignment of each specimen based on morphological characteristics.
- Locality: Geographic origin of the specimen, referring to the sampling sites described in Courville et al. (2025).
Table 2. Measurements of the length of three alveoli, from the anterior margin of the first alveolus to the posterior margin of the third (L3), compared with the width of the maxilla at the level of the fourth (W4) in various crocodylian species.
- Identification: Taxonomic assignment of each specimen based on morphological characteristics.
- Anatomical part: Anatomical identification of the different fragments analyzed (e.g., maxilla, premaxilla, dentary, skull).
- Collection number: The museum where the specimen was stored.
- L3: Measurements (in mm) of the length of three alveoli, from the anterior margin of the first alveolus to the posterior margin of the third (L3).
- W4: Measurements (in mm) of the width of the maxilla at the level of the fourth (W4).
- L3/W4: Ratio des mesures L3/W4.
Table 3. Measurements of the alveoli diameter compared with the distance between right-left alveolus according to their position on the maxilla or dentary in various crocodylian species.
- Identification: Taxonomic assignment of each specimen based on morphological characteristics.
- Collection number: The museum where the specimen was stored.
- Alveolus position: Position of the dental alveolus measured on the maxilla, premaxilla, or dentary. The alveolus number is indicated when it can be identified.
- Lateromedial diameter: Measurements (in mm) of the lateromedial diameter of the alveolus.
- Right-left alveolus distance: Measurement (in mm) of the distance between the right and left alveoli.