PAM 207 fossil assemblage supports early Turolian age for Moroccan basin site

A taxonomic and biochronological reassessment of 115 small-vertebrate fossils from Morocco’s PAM 207 site places the locality near the beginning of the early Turolian in North Africa. PAM 207 lies 773 metres above the base of the Amekchoud section in the Aït Kandoula Formation. The mammal-bearing interval is dominated by lacustrine carbonates with reversed magnetic polarity.

It is part of a basin fill exceeding 1,000 metres thick that comprises Neogene alluvial-fan to lacustrine sediments. The Ouarzazate Basin is an elongated Cenozoic foreland basin approximately 145 kilometres long and up to 35 kilometres wide, adjacent to the southern front of the High Atlas. The study is a morphological reassessment of material collected during a 2008 field campaign that targeted magnetostratigraphy and paleontology.

Four levels—PAM 135, 141, 207 and 209—were sampled, but only PAM 207 produced significant results. The collection comprises 14 fish teeth and bones, 86 disarticulated cranial and postcranial bones representing amphibians and squamate reptiles, and 15 identified small-mammal teeth from five taxa. Measurements were taken in millimetres using dental and osteological imaging, and fossils were compared with published specimens and modern comparative material.

All identifiable fish remains were assigned to Cyprinidae. Two pharyngeal teeth were attributed to Luciobarbus sp., three to Barbini indet., and a caudal vertebra and four palatine fragments to Cyprinidae indet.; four incomplete neural spines could not be identified more precisely. The absence of a complete pharyngeal arch prevented species-level identification of Luciobarbus.

The amphibian material, consisting mainly of juvenile and a few subadult individuals, was assigned to Discoglossinae indet. Its ilial morphology resembles Latonia and Latoglossus rather than modern Discoglossus, leaving open the possibility of Latoglossus zraus or an unidentified Latonia-like form. A single fragmentary parietal was attributed to Ophisaurus sp. sensu lato, although breakage and probable juvenile status prevented comparison among species.

Small-mammal identifications changed substantially during the reassessment. Two shrew teeth were identified as Lartetium africanum, with measurements within the reported range of specimens from Beni Mellal. Large ctenodactylid teeth were assigned to Africanomys sp., extending the genus’s known record beyond the Vallesian into the early Turolian.

Two gerbillids were revised as Zramys cf. salemi and Myocricetodon cf. ouaichi. Most consequential was the reassignment of murids from Paraethomys cf. miocaenicus to Progonomys mauretanicus: separation of the t6 and t9 on upper molars ruled out Paraethomys, while dimensions and diagnostic dental features supported P. mauretanicus. The revised rodent assemblage indicates that PAM 207 is slightly younger than the late Vallesian site of Guefaït 1, which contains Progonomys cathalai, and is close in age to the Algerian site of Sidi Salem, where P. mauretanicus and Zramys salemi co-occur.

PAM 207 and Sidi Salem also precede early Turolian localities containing Zramys cavatus. Tafna 2, with P. cathalai, is older, while Amama 2 at 7.7 million years ago contains Paraethomys, Zramys hamamai and Protatera algeriensis and is therefore younger. These bracketing relationships support the previously proposed correlation of PAM 207’s reversed polarity with C4r and allow the authors to reject correlations with C4Ar, dated to 9.78–9.10 million years ago, and C4n.1r, dated to 8.12–7.70 million years ago.

The revised framework tentatively places the lower limit of Biozone 3b near 11 million years ago, the boundary between Biozones 3b and 3c—and thus the onset of the early Turolian in North Africa—at approximately 8.7 million years ago, and the lower limit of Biozone 4b at about 7.7 million years ago. The 8.7-million-year estimate refers to the proposed boundary rather than a single precise age for PAM 207. The herpetofaunal composition is consistent with the rodent-based age assessment.

PAM 207 lacks tropical African amphibians found at older Moroccan localities, including Xenopus, Ptychadena and Sclerophrys regularis, as well as European taxa thought to have entered the Maghreb near the end of the Late Miocene. Instead, it contains the Eurasian-origin Discoglossinae and Ophisaurus, which the authors suggest may have reached North Africa during or before the Middle Miocene through the Early Miocene land connection between the Afro-Arabian plateau and Asia. The paleoenvironmental reconstruction is preliminary and qualitative, relying on the ecological requirements of the identified taxa and their closest living analogues.

Luciobarbus and the other cyprinids indicate temperate, slow-flowing freshwater environments such as rivers, lakes or swamps. Discoglossinae suggests water bodies that were permanent or seasonal and possibly slightly brackish, while Ophisaurus indicates some vegetative cover. The ctenodactylid and gerbillid rodents are associated with open, relatively arid settings.

Together, the fossils support an open, comparatively arid landscape with some vegetation alongside temperate freshwater habitats. This inference remains provisional because the sample is small, many elements are juvenile or incomplete, several taxonomic assignments are uncertain, and the ecological preferences of some extinct rodents are unknown.

Subject of Research: Taxonomic, biochronological and paleoenvironmental reassessment of the Late Miocene PAM 207 small-vertebrate assemblage in Morocco

Article Title: A new Late Miocene small vertebrate assemblage from the Ouarzazate Basin (High Atlas, Morocco) and its biochronological and paleoenvironmental significance

Article References: Piñero, P., Agustí, J., Blain, H.-A., Blanco-Lapaz, Á., Tesón, E., Teixell, A., & Furió, M. (2025). A new Late Miocene small vertebrate assemblage from the Ouarzazate Basin (High Atlas, Morocco) and its biochronological and paleoenvironmental significance. Fossil Record, 28(2), 377-395. https://doi.org/10.3897/fr.28.175508

Image Credits: AI Generated

DOI: 10.3897/fr.28.175508

Keywords: PAM 207, Ouarzazate Basin, Late Miocene, early Turolian, small vertebrates, biochronology, magnetostratigraphy, paleoenvironment, North Africa, fossil rodents, Late, Miocene