doi: 10.1098/rsos.172411. eCollection 2018 Jun.
A new fossil marine lizard with soft tissues from the Late Cretaceous of southern Italy
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- PMID:30110414
- PMCID: PMC6030324
- DOI: 10.1098/rsos.172411
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A new fossil marine lizard with soft tissues from the Late Cretaceous of southern Italy
Ilaria Paparella et al. R Soc Open Sci..
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Abstract
A new marine lizard showing exceptional soft tissue preservation was found in Late Cretaceous deposits of the Apulian Platform (Puglia, Italy).Primitivus manduriensis gen. et sp. nov. is not only the first evidence of the presence of dolichosaurs in a southern Italian Carbonate Platform, filling a palaeogeographic gap in the Mediterranean Tethys, but also extends the range of this group to the upper Campanian-lower Maastrichtian. Our parsimony analysis recovers a monophyletic non-ophidian pythonomorph clade, includingTetrapodophis amplectus at the stem of Mosasauroidea + Dolichosauridae, which together represent the sister group of Ophidia (modern and fossil snakes). Based on Bayesian inference instead, Pythonomorpha is monophyletic, with Ophidia representing the more deeply nested clade, and the new taxon as basal to all other pythonomorphs.Primitivus displays a fairly conservative morphology in terms of both axial elongation of the trunk and limb reduction, and the coexistence of aquatic adaptations with features hinting at the retention of the ability to move on land suggests a semi-aquatic lifestyle. The exceptional preservation of mineralized muscles, portions of the integument, cartilages and gut content provides unique sources of information about this extinct group of lizards. The new specimen may represent local persistence of a relict dolichosaur population until almost the end of the Cretaceous in the Mediterranean Tethys, and demonstrates the incompleteness of our knowledge of dolichosaur temporal and spatial distributions.
Keywords: Apulian Platform; Cretaceous; Pythonomorpha; Squamata; soft tissue; ultraviolet radiation.
Conflict of interest statement
We declare that we have no competing interests.
Figures
Holotype ofPrimitivus manduriensis gen. et sp. nov. (MPUR NS 161) at natural (a) and UV (b) light as exposed from the matrix in dorsal view. The imaging under UV radiations is a composite of two pictures, finalized with Adobe Photoshop CC 17 (2013 release). Scale bars: 5 cm.
Primitivus manduriensis MPUR NS 161 imaging of the skull at natural (a) and UV (b) light. The skull of the holotype is heavily crushed (a), and part of the elements are only preserved as impressions on the matrix, as observed under UV light (b), where the bone material still preserved is bright white. Reconstruction and interpretation of the cranial skeleton are presented in electronic supplementary material (figure S2). Scale bar: 1 cm.
Primitivus manduriensis MPUR NS 161 imaging of pectoral and pelvic girdles at natural (a,c) and UV (b,d) light. As visible from the photographs under UV radiation, the pectoral region is extensively covered by cartilage (b), surrounding both right scapula and coracoid, up to the humeral proximal epiphyses, which are invisible under natural light. For the sacral region, the white material visible under natural light anteriorly to both ischia and first sacral rib becomes purple when exposed to the UV radiation, as well as the scales on both sides of the hips. Reconstruction of both pectoral and pelvic girdles is provided in electronic supplementary material (figure S4). Scale bars: (a,b) 1 cm; (c,d) 2 cm.
Primitivus manduriensis MPUR NS 161 imaging of appendicular elements at natural (a,c,e,g) and UV (b,d,f,h) light. Both manus and pes, as well as most of the limb bones are preserved and mostly articulated. The forelimb autopodium is pictured here as seen under both natural (a,c) and long-wave UV radiations (b,d), where the soft tissues are differentiated by a pink–purple colour range. For the hindlimb autopodium (e–h) the images are taken under short-wave UV radiations (f,h), with the soft tissues spanning a grey colour scale. Reconstruction of the limbs is presented in electronic supplementary material (figures S5–S8). Scale bars: 2 cm.
Cartilages and gut content preserved in MPUR NS 161. Cartilaginous elements, like suprascapula (a,b), tracheal rings (arrows inc), bronchial rings (arrows ind) and sternum (d) are also preserved in the specimen, and their assessment was possible owing to the use of UV radiations (b,c,d,f). For the gut content (e,f), under UV light it is possible to differentiate between a hard tissue component (emphasized in white) and a soft tissue component (emphasized in pink-purple). Scale bars: 2 cm. Abbreviations: g, gut content; h, humerus; h-g, hard tissue component in the gut; pb, pubis; s-g, soft tissue component in the gut; ssc, suprascapula; strs, sternal ribs.
Different types of scales preserved inPrimitivus manduriensis. Integument and scale impressions are present on both sides of the trunk (a–d), around the limbs (e), and along the tail (f–h). The different types of dorsal scales vary from polygonal (a,c,e,g,h) to diamond-shaped (d), but in the subcaudal region of the tail they are transversally elongated (g,h). Among extant squamates, transversally elongated belly or subcaudal scales are typical of snakes, while among fossils, similar scales are found inPontosaurus kornhuberi. Arrows:b, pointing at the inner layer of the integument (dermis or hypodermis);f, pointing at scales of the caudal fin impressed on the matrix;g, pointing at body outline. Scale bars: (a) 2 cm; (c,e–h) 1 cm; (d) 5 mm.
Close-up ofPrimitivusmanduriensis MPUR NS 161 subcaudal scales. The proximal portion of the tail is exposed in dorsal view like the rest of the body, but at some point the tail rotates about 90° and the second part of the caudal column is exposed in left lateral view. Right after the torsion of the tail is where the transversally expanded ventral caudal scales (or subcaudals), similar to those of snakes, are visible. In snakes these scales can be present in a single row or as two adjacent rows; in MPUR NS 161, considering that this portion of the tail seems to be slightly twisted and compressed, we consider both interpretations as plausible. Scale bar: 1 cm.
Mineralized epaxial and hypaxial muscles preserved inPrimitivus manduriensis. Muscle fibres and bundles are well-recognizable along the posterior trunk, the pelvic girdle and the tail, even by the naked eye. Muscle fibres preserved between the first sacral vertebra and the left ischium (a–c) are about 30–35 µm in diameter. The muscle fibres along the anterior caudal region (d,f,g) are of the order of 10–15 µm. Under a compound microscope the single myomeres can in some instances also be distinguished (e). Scale bars: (a,d) 1 cm; (b) 5 mm; (c,e–g) 1 mm.
Results of SEM/EDX analyses for bony and soft tissues. Samples of hard and soft tissues have been selected in order to find their composition: a fragment of cortical bone from a trunk rib (a–c), and a sample from the muscles preserved along the trunk (d–f). Results for additional samples from the sediment and the gut content are reported in electronic supplementary material, figure S10. From the two spectra (c,f) it is clear that both bony and soft tissues have been permineralized with calcium phosphate, presenting the same composition. By comparison with Cosmidiset al. [68], the spherical forms visible in (d) and (e) can be interpreted as the presence of fossil bacteria. Bone vascularization is also perfectly preserved as visible on the bone fragment (a), and the diameter of the blood vessels is between 3.5 µm and 5 µm.
Primitivus manduriensis phylogenetic relationships based on parsimony. Phylogenetic hypotheses on the interrelationships of the new taxon are based on equal-weight maximum parsimony (a) and implied weighting maximum parsimony (b).
Primitivus manduriensis phylogenetic relationships based on Bayesian inference. The MCCT resulting from our model-based analysis recovers the new taxon as basal to all other pythonomorphs. The gradient colour of the branches is based on values of the posterior probabilities (numbers on each branch).
Primitivus manduriensis three-dimensional model and life reconstruction. The specimen is preserved in sediments deposited in the shallower portion of an inner lagoon of the Apulian Carbonate Platform, and is inferred to have a semi-aquatic lifestyle. Three-dimensional model (a) and life reconstruction (b) created by Fabio Manucci.
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