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.^[1] 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.^[2][3] This unit is known for its fossil content, including Invertertebrate and vertebrate ichnofossils and fossils.^[4][5]

Coimbra Formation
Stratigraphic range: Early to Late Sinemurian 199–188 Ma PreꞒ Ꞓ O S D C P T J K Pg N
S. Pedro de Muel Beach, the main outcrop
Type	Geological formation
Underlies	Água de Madeiros Formation
Overlies	Dagorda Formation
Area	Lusitanian Basin
Thickness	120-150 m
Lithology
Primary	Limestones
Location
Location	Coimbra Region
Coordinates	39.8° N, 9.0° W
Region	Lusitanian Basin
Country	Portugal
Type section
Named for	The Village of Coimbra
Thickness at type section	~120 m (390 ft)
Coimbra Formation (Portugal)

Paleoenvironment

Stratigraphic column of the Lusitanian Basin

The sediments in the Coimbra Formation represent the shallow sections of an inner carbonate platform, adjacent to the Paleozoic basement in the E.^[6] 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.^[1] 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.^[7] 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.^[6] 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.^[8] 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.^[8] 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.^[8] 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.^[6] The recent discovery of Dinosaur tracks revelated the presence of supratidal environments located in a shallow, tropical coastal area, likely near the shore.^[4]

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[9]	A. spp.	Sao Pedro de Muel	Isolated shells	An Ammonite of the family Asteroceratidae	Reconstruction
Boehmiola[10][11]	B. exilis	Sao Pedro de Muel	Isolated shells	A Gastropod of the family Ceritellidae
Ceratomya[12]	C. cf. petricosa	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Ceratomyidae
Epophioceroides[9]	E. apertus E. spp.	Sao Pedro de Muel	Isolated shells	An Ammonite of the family Asteroceratidae
Gagaticeras[1]	G. spp.	Sao Pedro de Muel	Isolated shells	An Ammonite of the family Echioceratidae
Mactromya[1][12]	M. cardioides M. spp.	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Mactromyidae
Microschiza[11]	M. spp.	Praia Polvoeira Sao Pedro de Muel	Isolated shells	A Gastropod of the family Purpurinidae
Nerinella[11]	N. ficalhoi	Penedo da Saudade	Isolated shells	A Gastropod of the family Nerinellidae
Oonia[11]	O. casta	Praia  da  Concha	Isolated shells	A Gastropod of the family Pseudomelaniidae
Ostrea[10]	O. sublamellosa	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Ostreidae	Example of specimen
Oxynoticeras[1]	O. spp.	Sao Pedro de Muel	Isolated shells	An Ammonite of the family Oxynoticeratidae
Pachymya[12]	P. (Arcomya) oblonga	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Pholadomyidae
Pholadomya[1][12]	P. (Pholadomya) voltzii P. (Pholadomya) ambigua P. spp.	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Pholadomyidae	Example of specimen
Pleuromya[12]	P. uniformis P. galathea	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Pleuromyidae	Example of specimen
Pseudokatosira[11]	P.? aff. undulata P. spp.	Palheira Sao Pedro de Muel	Isolated shells	A Gastropod of the family Zygopleurinae
Pseudomelania[5][11]	P. costae P. ssp.	Praia Polvoeira Sao Pedro de Muel	Isolated shells	A Gastropod of the family Pseudomelaniidae
Ptycharietites[9]	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[1][10]	U. costae	Sao Pedro de Muel	Isolated shells	A Bivalve of the family Mactromyidae

Crustacea

Genus	Species	Location	Material	Notes	Images
Donzocythere[13]	D. cf. D. convergeas	Sao Pedro de Muel	Isolated Carapaces & Valves	A marine ostracodan member of the family Cythereinae
Ektyphocythere[13]	E. retia E. lacunosa E. sinemiurana	Sao Pedro de Muel	Isolated Carapaces & Valves	A marine ostracodan member of the family Progonocytherinae
Klieana[13]	K.? coimbraensis	Praia da Concha	Isolated Carapaces & Valves	A brackish marine ostracodan member of the family Cythereinae
Klinglerella[13]	"K." roselinae	Praia da Concha	Isolated Carapaces & Valves	A marine ostracodan member of the family Progonocytherinae
Ljubimovella[13]	L.? frequens	Sao Pedro de Muel	Isolated Carapaces & Valves	A marine ostracodan member of the family Cythereinae. The Second most abundant genus
Lutkevichinella[13]	L. hortonae	Sao Pedro de Muel	Isolated Carapaces & Valves	A brackish marine ostracodan member of the family Limnocytheridae
Marslatourella[13]	M. aff. M. heitoufensis	Sao Pedro de Muel	Isolated Carapaces & Valves	A marine ostracodan member of the family Cythereinae
Monoceratina[13]	M. sp.	Sao Pedro de Muel	Isolated Carapaces & Valves	A marine ostracodan member of the family Bythocytheridae
Phraterfabanella[13]	P. boomeri	Praia da Concha	Isolated Carapaces & Valves	A brackish marine ostracodan member of the family Cythereinae. Also recorded on the Rotzo Formation
Pseudomacrocypris[13]	P. cf. P. subtriangularis	Praia da Concha	Isolated Carapaces & Valves	A marine ostracodan member of the family Macrocyprididae
Tropacythere[13]	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[14]	C. cor	Papôa-Portinho da Areia Sao Pedro de Muel	Isolated shells	A Branchiopod of the family Zeilleriidae
Cuersithyris[14]	C. gijonensis	Papôa-Portinho da Areia Sao Pedro de Muel	Isolated shells	A Branchiopod of the family Lobothyrididae
Lobothyris[14]	L. sinemuriensis	Papôa-Portinho da Areia Sao Pedro de Muel	Isolated shells	A Branchiopod of the family Lobothyrididae
Merophricus?[1][14]	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[14]	T. dunrobinensis T. ranina	Papôa-Portinho da Areia Sao Pedro de Muel	Isolated shells	A Branchiopod of the family Tetrarhynchiidae
Zeilleria[1][14]	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[5]	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.^[15]

Genus	Species	Location	Material	Notes	Images
Batrachopus[4]	B. isp.	Campo de Alvaiázere	Footprints	Tracks referred to Crocodylomorpha, maybe marine Teleosauridae
Lusitanosaurus[16]	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[4]	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

See also

• List of dinosaur-bearing rock formations

• Blue Lias, England
• Charmouth Mudstone Formation, England
• Zagaje Formation, Poland
• Drzewica Formation, Poland
• Ciechocinek Formation, Poland
• Borucice Formation, Poland
• Rotzo Formation, Italy
• Saltrio Formation, Italy
• Moltrasio Formation, Italy
• Marne di Monte Serrone, Italy
• Calcare di Sogno, Italy
• Podpeč Limestone, Slovenia
• El Pedregal Formation, Spain
• Aganane Formation, Morocco
• Tafraout Group, Morocco
• Azilal Formation, Morocco
• Budoš Limestone, Montenegro
• Kota Formation, India
• Cañadón Asfalto Formation, Argentina
• Los Molles Formation, Argentina
• Kandreho Formation, Madagascar
• Elliot Formation, South Africa
• Clarens Formation, South Africa
• Evergreen Formation, Australia
• Cattamarra Coal Measures, Australia
• Hanson Formation, Antarctica
• Mawson Formation, Antarctica

References

1. Duarte, Luís Vítor; Silva, Ricardo Louro; Azerêdo, Ana Cristina; Comas-Rengifo, María José; Mendonça Filho, João Graciano (2023-01-13). "Shallow-water carbonates of the Coimbra Formation, Lusitanian Basin (Portugal): contributions to the integrated stratigraphic analysis of the Sinemurian sedimentary successions in the western Iberian Margin". Comptes Rendus. Géoscience. 354 (S3): 89–106. doi:10.5802/crgeos.144. ISSN 1778-7025.
2. Duarte, L. V.; Soares, A. F. (2002). "Litostratigrafia das séries margo-calcárias do Jurássico inferior da Bacia Lusitânica (Portugal)" (PDF). Com. Instituto Geológico e Mineiro. 89 (1): 135–154.
3. Duarte, L. V.; Silva, R. F. L.; Oliveira, L. V.; Rengifo, M. J. C.; Silva, F. (2010). "Organic-rich facies in the Sinemurian and Pliensbachian of the Lusitanian Basin, Portugal: Total Organic Carbon distribution and relation to transgressive-regressive facies cycles". Geologica Acta: 325–340.
4. Figueiredo, Silvério D.; de Carvalho, Carlos Neto; Cunha, Pedro P.; Duarte, Luís V.; Fonseca, Alexandre; Monteiro, Cláudio; Forte, João (2023-09-20). "The first dinosaurs in Iberia: a new dinosaur tracksite from the Sinemurian (Lower Jurassic) of Portugal". Historical Biology: 1–14. doi:10.1080/08912963.2023.2256751. ISSN 0891-2963.
5. Puértolas-Pascual, Eduardo; Marx, Miguel; Mateus, Octávio; Saleiro, André; Fernandes, Alexandra; Marinheiro, João; Tomás, Carla; Mateus, Simão (2021). "A new plesiosaur from the Lower Jurassic of Portugal and the early radiation of Plesiosauroidea". Acta Palaeontologica Polonica. 66. doi:10.4202/app.00815.2020. hdl:10362/123694. ISSN 0567-7920.
6. Poças Ribeiro, N.; Mendonça Filho, J.G.; Duarte, L.V.; Silva, R.L.; Mendonça, J.O.; Silva, T.F. (2013). "Palynofacies and organic geochemistry of the Sinemurian carbonate deposits in the western Lusitanian Basin (Portugal): Coimbra and Água de Madeiros formations". International Journal of Coal Geology. 111: 37–52. doi:10.1016/j.coal.2012.12.006. ISSN 0166-5162.
7. Correia, G. G.; Duarte, L. V.; Pereira, A.; Silva, R. L. (2013-02-15). "Outcrop gamma-ray spectrometry: Applications to the Sinemurian–Pliensbachian organic-rich facies of the Lusitanian Basin (Portugal)". Journal of Iberian Geology. 38 (2). doi:10.5209/rev_jige.2012.v38.n2.40464. ISSN 1886-7995.
8. Azerêdo, Ana C.; Silva, Ricardo L.; Duarte, Luís V.; Cabral, M. Cristina (2009-09-11). "Subtidal stromatolites from the Sinemurian of the Lusitanian Basin (Portugal)". Facies. 56 (2): 211–230. doi:10.1007/s10347-009-0198-0. ISSN 0172-9179.
9. Dommergues, J.L.; Meister, C.; Rocha, R. B. (2010). "The Sinemurian ammonites of the Lusitanian Basin (Portugal): an example of complex endemic evolution". Palaeodiversity. 3 (59–87).
10. Mouterde, R.; Rocha, R. B.; Delance, J. (1981). "Atlas des fossiles caractéristiques du Lias portugais". Ciências da Terra/Earth Sciences Journal. 6: 49–76.
11. Vitón, Íñigo; Comas-Rengifo, María José; Ricardo Paredes, Ricardo (2020-12-14). "Early Jurassic (Sinemurian) gastropods from the Lusitanian Basin (west of Portugal)". Spanish Journal of Palaeontology. 35 (2): 147–166. doi:10.7203/sjp.35.2.18478. ISSN 2660-9568.
12. Paredes, R.; Comas-Rengifo, and, M. J.; Duarte, L. V. (2013). "Moluscos bivalves da Formação de Água de Madeiros (Sinemuriano superior) da Bacia Lusitânica (Portugal)" (PDF). Comunicações Geológicas. 100 (1): 21–27.
13. Cabral, M. Cristina; Colin, Jean-Paul; Azeredo, Ana C.; Silva, Ricardo L.; Duarte, Luis V. (2015). "Brackish and marine ostracode assemblages from the Sinemurian of western Portugal, with descriptions of new species". Micropaleontology. 61 (1–2): 3–24. doi:10.47894/mpal.61.1.02. ISSN 0026-2803.
14. Paredes, R.; Comas-Rengifo, M. J.; Duarte, L. V.; Goy, A.; Paredes, R.; Comas-Rengifo, M. J.; Duarte, L. V.; Goy, A. (2013). "Braquiópodes do Sinemuriano superior da região de S. Pedro de Moel e de Peniche (Bacia Lusitânica, Portugal)". Comunicacoes Geologicas. 100 (SPEC.ISS.1): 29–35. ISSN 0873-948X.
15. Lusa (2025-02-19). "Fóssil de dinossauro com mais de 190 milhões de anos descoberto na praia de Água de Madeiros". PÚBLICO (in Portuguese). Retrieved 2025-02-19.
16. Lapparent, A. F. d.; Zbyszewski, G. (1951). "Un Stégosaurien nouveau dans le Lias du Portugal [A new stegosaurian in the Lias of Portugal]". Boletim do Museu e Laboratório Mineralógico e Geológico, Faculdade de Ciências da Universidade de Lisboa. 19 (6): 107–108.