# Coimbra Formation

The Coimbra Formation (Also known as Camadas de Coimbra or Calcários de S. Miguel) is a geological formation of Sinemurian (Lower Jurassic) age in the Lusitanian Basin of Portugal. The unit represents a series of peritidal to intertidal facies of a Carbonate platform mostly of Obtusum–Oxynotum age, that gradually evolve to open marine/hemipelagic units Vale das Fontes Formation and Lemede formation. This unit is known for its fossil content, including Invertertebrate and vertebrate ichnofossils and fossils.

## Paleoenvironment

The sediments in the Coimbra Formation represent the shallow sections of an inner carbonate platform, adjacent to the Paleozoic basement in the E. They are rich in organic matter and are found alongside marl layers in a shallow marine setting. The organic material is divided into three groups (A, B, and C), showing how it is spread across different layers. The middle section mainly consists of group B, with a lot of microbial mat particles and very few plant particles. This layer has the highest level of Total organic carbon (TOC), indicating it was deposited in a restricted and stagnant area with little water movement. In the upper section, all three groups (A, B, and C) are present. The lower part of this section contains more plant debris and fewer marine particles, suggesting a stronger influence from land and more oxygen in the environment, leading to lower TOC levels. As we move up, group B shows a reduced land influence. At the top, group A takes over, with more marine particles and fewer plant materials, suggesting a transition to a more open marine environment. Overall, the Coimbra Formation is made up of shallow marine deposits formed in a low-energy setting, with occasional stronger events like storms or floods. The area was a calm, shallow marine environment with limited water flow. Most sediments were fine-grained, showing low-energy conditions and a semi-arid climate. Microbialites formed during periods of slow sediment buildup, indicating low water movement. Occasional storms brought better oxygenated water, supporting brief marine life bursts. Fossils suggest shifts between restricted and open marine environments due to minor sea-level changes. Over time, open-marine conditions increased, with more typical marine fossils reflecting a significant rise in sea level. Individual Stromatolite mounds are clearly defined, either as separate structures lined up next to each other or as irregular, flat to wavy layers that merge at the base. Palynology includes Classopollis (Cheirolepidiaceae Conifer) and Botryococcus as the dominant continental components, while marine palynomorphs include the genera Tasmanites and Cymathiosphaera (Prasinophyte algae) as well Zygnemataceae. The recent discovery of Dinosaur tracks revelated the presence of supratidal environments located in a shallow, tropical coastal area, likely near the shore.

## Fossil Content

| Color key Taxon Reclassified taxon Taxon falsely reported as present Dubious taxon or junior synonym Ichnotaxon Ootaxon Morphotaxon | Notes Uncertain or tentative taxa are in small text; crossed out taxa are discredited. |

### Mollusca

| Genus | Species | Location | Material | Notes | Images |
| Asteroceras | A. spp. | Sao Pedro de Muel | Isolated shells | An Ammonite of the family Asteroceratidae | Reconstruction |
| Boehmiola | B. exilis | Sao Pedro de Muel | Isolated shells | A Gastropod of the family Ceritellidae | |
| Ceratomya | C. cf. petricosa | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Ceratomyidae | |
| Epophioceroides | E. apertus E. spp. | Sao Pedro de Muel | Isolated shells | An Ammonite of the family Asteroceratidae | |
| Gagaticeras | G. spp. | Sao Pedro de Muel | Isolated shells | An Ammonite of the family Echioceratidae | |
| Mactromya | M. cardioides M. spp. | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Mactromyidae | |
| Microschiza | M. spp. | Praia Polvoeira Sao Pedro de Muel | Isolated shells | A Gastropod of the family Purpurinidae | |
| Nerinella | N. ficalhoi | Penedo da Saudade | Isolated shells | A Gastropod of the family Nerinellidae | |
| Oonia | O. casta | Praia da Concha | Isolated shells | A Gastropod of the family Pseudomelaniidae | |
| Ostrea | O. sublamellosa | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Ostreidae | Example of specimen |
| Oxynoticeras | O. spp. | Sao Pedro de Muel | Isolated shells | An Ammonite of the family Oxynoticeratidae | |
| Pachymya | P. (Arcomya) oblonga | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Pholadomyidae | |
| Pholadomya | P. (Pholadomya) voltzii P. (Pholadomya) ambigua P. spp. | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Pholadomyidae | Example of specimen |
| Pleuromya | P. uniformis P. galathea | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Pleuromyidae | Example of specimen |
| Pseudokatosira | P.? aff. undulata P. spp. | Palheira Sao Pedro de Muel | Isolated shells | A Gastropod of the family Zygopleurinae | |
| Pseudomelania | P. costae P. ssp. | Praia Polvoeira Sao Pedro de Muel | Isolated shells | A Gastropod of the family Pseudomelaniidae | |
| Ptycharietites | P. asteroceroides P. ("subgen. indet. B") muellense P. (Ptycharietites) heterogenus P. (Pompeckiocreas) cf. oncocephalus P. (Ptycharietites) ptychogenos P. spp. | Sao Pedro de Muel | Isolated shells | An Ammonite of the family Asteroceratidae | |
| Unicardium | U. costae | Sao Pedro de Muel | Isolated shells | A Bivalve of the family Mactromyidae | |

### Crustacea

| Genus | Species | Location | Material | Notes |
| Donzocythere | D. cf. D. convergeas | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Cythereinae |
| Ektyphocythere | E. retia E. lacunosa E. sinemiurana | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Progonocytherinae |
| Klieana | K.? coimbraensis | Praia da Concha | Isolated Carapaces & Valves | A brackish marine ostracodan member of the family Cythereinae |
| Klinglerella | "K." roselinae | Praia da Concha | Isolated Carapaces & Valves | A marine ostracodan member of the family Progonocytherinae |
| Ljubimovella | L.? frequens | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Cythereinae. The Second most abundant genus |
| Lutkevichinella | L. hortonae | Sao Pedro de Muel | Isolated Carapaces & Valves | A brackish marine ostracodan member of the family Limnocytheridae |
| Marslatourella | M. aff. M. heitoufensis | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Cythereinae |
| Monoceratina | M. sp. | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Bythocytheridae |
| Phraterfabanella | P. boomeri | Praia da Concha | Isolated Carapaces & Valves | A brackish marine ostracodan member of the family Cythereinae. Also recorded on the Rotzo Formation |
| Pseudomacrocypris | P. cf. P. subtriangularis | Praia da Concha | Isolated Carapaces & Valves | A marine ostracodan member of the family Macrocyprididae |
| Tropacythere | T. normaniae | Sao Pedro de Muel | Isolated Carapaces & Valves | A marine ostracodan member of the family Progonocytherinae |

### Brachiopoda

| Genus | Species | Location | Material | Notes | Images |
| Cincta | C. cor | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Zeilleriidae | |
| Cuersithyris | C. gijonensis | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Lobothyrididae | |
| Lobothyris | L. sinemuriensis | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Lobothyrididae | |
| Merophricus? | M.? (Terebratula?) ribeiroi | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Plectoconchidae or Terebratulidae | Specimen of the genus |
| Tetrarhynchia | T. dunrobinensis T. ranina | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Tetrarhynchiidae | |
| Zeilleria | Z. quiaiosensis Z. ssp. | Papôa-Portinho da Areia Sao Pedro de Muel | Isolated shells | A Branchiopod of the family Zeilleriidae | |

### Plesiosauria

| Genus | Species | Location | Material | Notes | Images |
| Plesiopharos | P. moelensis | Praia da Concha | ML2302 a partial skeleton belonging to a single individual | A Plesiosaur, possible member of Plesiosauroidea | Plesiopharos reconstruction |

### Archosauria

In February 2025 it was announced the discovery of Dinosaur remains within Água de Madeiros beach, excavated in 2024, extracted in a block weighing around 1200 kilos.
| Genus | Species | Location | Material | Notes | Images |
| Batrachopus | B. isp. | Campo de Alvaiázere | Footprints | Tracks referred to Crocodylomorpha, maybe marine Teleosauridae | |
| Lusitanosaurus | L. liasicus | Sao Pedro de Muel | Single partial left maxilla | An Indeterminate Archosaur, previously thought to be a Thyreophoran dinosaur. Its exact provenance is unknown | |
| Moyenisauropus | M. lusitanicus | Campo de Alvaiázere | Footprints | Tracks referred to the Dinosaurian group Thyreophora, probably from a taxon similar to Scelidosaurus. | Scelidosaurus, a possible relative of the Moyenisauropus trackmaker |