Tartarugas e Dinossauros do Cretácico Inferior da Formação do Papo-Seco (Barremiano Inferior) em Areias do Mastro (Cabo Espichel, Portugal): Geologia, Resultados Paleontológicos e Implicações Paleoecológicas

• Silvério Figueiredo
• ORCID - 0000-0002-6197-375X
• Instituto Politécnico de Tomar, Quinta do Contador – Estrada da Serra, 2300-313 Tomar, Portugal | Centro Português de Geo-História e Pré-História, Largo de São Caetano, 2150-265 Golegã, Portugal | Centro de Geociências Universidade de Coimbra, Polo II–Rua Sílvio Lima, 3030-790 Coimbra, Portugal
• Alice Duraud
• ORCID - 0009-0009-1129-8539
• Centro Português de Geo-História e Pré-História, Largo de São Caetano, 2150-265 Golegã, Portugal

• Língua: Português
• DOI: doi.org/10.82151/CPGP.BArt.00050

• Palavras-chave:
  Tartarugas; Dinossauros; Cretácico Inferior; Barremiano; Cabo Espichel; Paleoecologia; Bacia Lusitânica.
• Resumo:
  Descrevem-se e interpretam-se restos fósseis de tartarugas e dinossauros e outros vertebrados provenientes dos níveis basais da Formação do Papo-Seco (Barremiano Inferior, Cretácico Inferior), expostos na arriba costeira de Areias do Mastro, a norte do Cabo Espichel (Sesimbra, Portugal). Estes materiais integram um conjunto mais amplo de vertebrados e invertebrados recolhidos ao longo de várias campanhas de campo realizadas entre 1998 e 2016 pelo Centro Português de Geo-História e Pré-História. A análise sedimentológica indica deposição num sistema transicional lagunar–estuarino com evolução para ambiente costeiro marinho mais aberto. Os restos de tartarugas e dinossauros assumem particular relevância paleoecológica e tafonómica, contribuindo de forma significativa para o conhecimento da paleodiversidade vertebrada do Cretácico Inferior da Bacia Lusitânica.

• Key-words:
  Turtles; Dinosaurs; Lower Cretaceous; Barremian; Cabo Espichel; Paleoecology; Lusitanian Basin.
• Expanded Abstract:
  Fossil remains of turtles, dinosaurs and other vertebrates from the basal levels of the Papo-Seco Formation (Lower Barremian, Lower Cretaceous), exposed along the coastal cliffs of Areias do Mastro, north of Cabo Espichel (Sesimbra, Portugal), are described and interpreted. These materials form part of a broader assemblage of vertebrates and invertebrates collected during several systematic field campaigns conducted between 1998 and 2016 by the Centro Português de Geo-História e Pré-História (CPGP). The fossil assemblage comprises 48 specimens, including fragmentary remains of Testudines (shell plates, plastron elements, vertebrae, humeri, and a well-preserved skull), Theropoda indet. and Baryonyx sp. (isolated teeth and bone fragments), Iguanodontoidea indet. and Sauropoda indet. (fragmentary appendicular and axial elements), Crocodylomorpha cf. Anteophthalmosuchus (teeth), Lepidotes (crushing teeth), and Pterosauria (Ornithocheiridae indet. and Ctenochasmatoidea indet.), associated with a diverse invertebrate fauna including bivalves (Nipponomaia, Eomiodon) and gastropods (Naticidae, Chemnitzia, Turritella).
  Sedimentological analysis of the approximately 18.5 m thick succession indicates deposition within a transitional lagoonal–estuarine system that evolved toward a more open coastal marine environment under transgressive conditions. Three main depositional units are recognized: a lower clayey unit representing restricted lagoonal settings, an intermediate transitional lagoonal–estuarine unit with increasing sand content and tidal influence, and an upper sandy unit indicative of higher-energy open marine coastal conditions. Fossil distribution throughout this succession reveals distinct taphonomic patterns: turtle and fish remains occur consistently across all units, suggesting autochthonous to parautochthonous preservation in stable aquatic habitats, whereas dinosaur remains are predominantly restricted to the upper sandy levels, indicating allochthonous transport from adjacent terrestrial environments during high-energy episodic events.
  The turtle and dinosaur remains are of particular paleoecological and taphonomic significance. The presence of both marine-adapted (Plesiochelyidae) and freshwater (Sinemydidae) turtle lineages documents hydrological connectivity between coastal marine and fluvial systems, while the occurrence of Baryonyx sp. confirms the presence of specialized piscivorous predators within these estuarine ecosystems. The well-preserved turtle skull represents one of the few cranial specimens known from Lower Cretaceous deposits in Portugal, offering significant potential for systematic and paleobiological studies. The fragmentary but taxonomically diverse dinosaur material, including ornithopod and sauropod elements, provides evidence for the proximity of diverse terrestrial herbivore communities and their episodic incorporation into coastal depositional systems.
  These findings contribute substantially to the understanding of vertebrate paleodiversity in the Lower Cretaceous of the Lusitanian Basin, documenting a structured trophic pyramid with invertebrates at the base, fishes and turtles at intermediate levels, and crocodilomorphs, pterosaurs and theropod dinosaurs as apex predators. The integrated sedimentological and paleontological data establish the Areias do Mastro succession as a key reference section for studying faunal transitions in Wealden-type deposits of the Iberian Peninsula, highlighting the importance of estuarine environments as biodiversity hotspots and taphonomic windows into Early Cretaceous terrestrial ecosystems. Furthermore, the CPGP collection represents one of the most comprehensively documented vertebrate assemblages from the Papo-Seco Formation, providing a foundation for future systematic revisions, isotopic paleoecological studies, and comparisons with contemporary faunas from other European localities.