taxonID	type	description	language	source
03EB87A8FFC0FFB582305AC7A0BEFBFD.taxon	description	Figs. 1 - 2	en	Cretaceous, Late, Pasini, Lebanon Giovanni, Garassino, Alessandro (2023): Short Communication Evidence of mysid swarm behaviour (Crustacea: Malacostraca) from the Cenomanian (Late Cretaceous) of Hakel, Lebanon. Natural History Sciences 10 (1): 75-78, DOI: 10.4081/nhs.2023.625, URL: http://dx.doi.org/10.4081/nhs.2023.625
03EB87A8FFC0FFB582305AC7A0BEFBFD.taxon	materials_examined	Material and measurements: Over 150 specimens poorly preserved on a sublithographic limestone slab (MSNM i 29340: c. 130 x 230 mm), mostly overlapped each other, in dorsal, ventral and lateral views. Only sevisible the last four thoracic somites; the thorax composed by eight thoracic somites; and the pleon with six somites, allow us to assign the studied specimens to the Mysidacea and, according to Meland et al. (2015) to the Mysida Boas 1883, based on the morphological generic characters of the carapace and absence of a long protruding rostrum and pointed spines on the lower lateral posterior margins, characters typical of the Lophogastrida Boas 1883. Uropodal statocyst (balance organ in the endopod of the uropods) is not clearly visible in the studied specimens (as preserved) (Meland et al., 2015: Fig. 1). Moreover, it is hard to identify other characters of the studied specimens, such as the cephalic, thoracic, and pleonal thin appendages due to the poor state of preservation. The possible absence of uropodal endopod statocyst could be a character shared with the representatives of the Petalophthalmidae Czerniavsky 1882, including mainly extant bathypelagic species. However, this datum does not match with the palaeoenvironmental reconstruction for the Hakel limestone, considered as probably deposited in small, shallow basins comprising intra-shelf depressions (Charbonnier et al., 2017: 17). In any case, the lack of other distinctive characters makes a precise assignment of the studied specimens very difficult and uncertain. The swarm aggregation seems to include specimens with two different morphological characters: a first and more common having sub-ovoid carapace and relatively short pleon (type 1) and a second, less common, with more slender, ellipsoidal carapace (as preserved) and more elongate pleon (type 2) (Fig. 2 B). These two typologies could be interpreted as 1) different kind of compression / distortion of the body during the diagenesis; 2) intraspecific sexual variability; 3) presence of different growth stages within the aggregation; 4) presence of two different taxa within Mysida sharing the same fossil palaeoenvironment. The lacking of substantial characters useful for a closer comparison with fossil and extant species leaves open the question. Mass mortality events are not uncommon from the Hakel laminate layers, interpreted as due to rhythmic or seasonal occurrence of catastrophic events (anoxia or disoxia) in the basin waters (Pasini & Garassino, 2010: 8). Similar slabs with these peculiar crustacean assemblages were previously reported by Pasini & Garassino (2010), and regarded as a fossil evidence of the schooling behaviour of indeterminate macruran decapod, probably preadults penaeidean and caridean shrimps and of other minor groups of crustaceans (possibly including also mysidaceans).	en	Cretaceous, Late, Pasini, Lebanon Giovanni, Garassino, Alessandro (2023): Short Communication Evidence of mysid swarm behaviour (Crustacea: Malacostraca) from the Cenomanian (Late Cretaceous) of Hakel, Lebanon. Natural History Sciences 10 (1): 75-78, DOI: 10.4081/nhs.2023.625, URL: http://dx.doi.org/10.4081/nhs.2023.625
