The Montsec collection in this institution includes an extraordinary representation of fossil fish and plants, as well as relevant specimens of insects, crustaceans and amphibians.
The collection includes the type of the pycnodontiform fish Coelodus (Ocloedus) subdiscus, two diptera Hirmoneura Richterae and Hirmoneura (Eohirmoneura) in them, two hymenoptera Ilerdosphex wenzi and Pompilopterus montsecensis, the conifer Nageiopsis hispanica.
The enigmatic frog Eodiscoglossus santonjae, although represented by eight specimens, still maintains its unresolved phylogenetic position (Vergnaud-Grazzini and Wenz 1975; Báez & Gómez 2016).
As for insects, there is a good representation of mayflies, of various adult forms of the fly Mesopalingea leridae, as well as some nymphs. There are also specimens identified as fragments of the thorax and abdomen of indeterminate wasps.
A large part of fossil plants are preserved in the form of traces of vegetative and reproductive organs, in many cases fragmented. They include the type (holotype) of one of the oldest angiosperms, the aquatic species Ranunculus ferreri (Blanc-Louvel 1984), and several specimens of another angiosperm are also referred to, Montsechia vidalii , and the conifers of the genera Aracaurites , Podozamites , Brachyphyllum , Pagiophyllum and Frenelopsis .