The natural endocast Museo di Geologia e Paleontologia of the Università degli Studi di Torino (MGPT)‐PU 13873 is described and analyzed in order to interpret its taxonomic affinities and its potential significance on our understanding of cetacean brain evolution. The endocast is from the early Miocene of Piedmont (between ca. 19 and 16 million years ago), Northwestern Italy, and shows a number of plesiomorphic characters. These include: scarcely rounded cerebral hemispheres, cerebellum exposed in dorsal view with little superimposition by the cerebral hemispheres, short temporal lobe, and long sylvian fissure. The distance between the hypophysis and the rostral pons is particularly high, as it was determined by the calculus of the hypothalamus quotient, suggesting that the development of a deep interpeduncular fossa was not as advanced as in living odontocetes. The encephalization quotient (EQ) of MGPT‐PU 13873 is ~1.81; therefore, this specimen shows an EQ in line with other fossil whales of the same geological age (early Miocene). Comparative analysis shows that there is a critical lack of data from the late Miocene and Pliocene that prevents us to fully understand the recent evolution of the EQ diversity in whales. Moreover, the past diversity of brain size and shape in mysticetes is virtually unknown. All these observations point to the need of additional efforts to uncover evolutionary patterns and processes on cetacean brain evolution.
Abstract:Compressions of fossil leaves on marl blocks soaked with water are tricky palaeobotanic findings to deal with. In fact, this peculiarity makes the findings exposed to serious degradation: the evaporation of water causes shrinkage of the matrix and the leaf leading to fragmentation, delamination and exfoliation of the fossil, until its final disappearance. The aim of this research was to identify a consolidation method which satisfies museum needs and can be utilised for all conditions of hydration of the object. Following a survey of several natural science museums in Northern Italy, Paraloid™ B72 and PEG4000 along with other resins never previously used on this kind of fossil were tested. At the end of the research, two products gave adequate or good results, preserving the leaf from further degradation whatever the hydration condition of the object: the acrylic resin Paraloid™ B72 and a polyurethane resin.
Marzanoptera tersillae gen. & sp. nov., a new balaenopterid from the Pliocene of the Piedmont in north-west Italy, is described based on a partial skeleton and compared with other living and fossil baleen whales. Marzanoptera tersillae shares characters, such as the shape of the supraoccipital, glenoid fossa of the squamosal and zygomatic process of the squamosal, with ‘Balaenoptera’ bertae. We used a computed tomography scan to view parts of the skull that were otherwise impossible to observe, such as the periotic. A phylogenetic analysis based on 355 character states scored from 87 taxa revealed a well-resolved hypothesis of relationships for Balaenopteridae and a general phylogenetic hypothesis for chaeomysticetes. The monophyly of all superfamily- and family-rank clades and of crown balaenopterid species was confirmed. In addition, a monophyletic group including most basal thalassotherian taxa was recovered. The mollusc fauna associated with the specimen was autochtonous and constituted a residual fossil assemblage indicative of an environmental context located below the base of the storm wave, characterized by a low-energy hydrodynamic regimen. Many shark teeth have been found in close association or embedded within the bones, suggesting a possible scavenging action by two shark species on the whale carcass.
The discovery of an early Miocene chaeomysticete from the Pietra da Cantoni Group in Piedmont (northwestern Italy) allowed for the establishment of Atlanticetus lavei gen. et sp. nov. The new species is represented by a partial skeleton including the periotic and tympanic bullae and has an anatomical resemblance to Atlanticetus patulus (comb. nov.) from the western North Atlantic. The early Miocene age of the new specimen supports the view that it represents the oldest record of Chaeomysticeti from the Mediterranean. A new phylogenetic analysis showed that both A. patulus and A. lavei belong to a radiation of basal thalassotherian taxa. The basal thalassotherians are monophyletic to the exclusion of Cetotheriidae and Balaenopteroidea. The reconstruction of ancestral characters at selected nodes indicates that the group including Atlanticetus and living balaenopterid taxa independently evolved rostra wide at the base, an anterolateral expansion in the tympanic bulla, and a peculiar arrangement of the endocranial foramina of the periotic, exhibiting a noteworthy phenomenon of convergent evolution in feeding and hearing functions with Balaenopteridae. Palaeobiogeographical analysis shows that the North Pacific was the centre of origin of Balaenomorpha (crown mysticetes), Thalassotherii and Balaenoidea. The recurrent invasion of the Mediterranean by balaenomorph mysticetes occurred from both the North Atlantic and North Pacific.
Baleen whales are considered underencephalized mammals due to their reduced brain size with respect to their body size (encephalization quotient [EQ] << 1). Despite their low EQ, mysticetes exhibit complex behavioral patterns in terms of motor abilities, vocal repertoire, and cultural learning. Very scarce information is available about the morphological evolution of the brain in this group; this makes it difficult to investigate the historical changes in brain shape and size in order to relate the origin of the complex mysticete behavioral repertoire to the evolution of specific neural substrates. Here, the first description of the virtual endocast of a fossil balaenopterid species, <i>Marzanoptera tersillae</i> from the Italian Pliocene, reveals an EQ of around 3, which is exceptional for baleen whales. The endocast showed a morphologically different organization of the brain in this fossil whale as the cerebral hemispheres are anteroposteriorly shortened, the cerebellum lacks the posteromedial expansion of the cerebellar hemispheres, and the cerebellar vermis is unusually reduced. The comparative reductions of the cerebral and cerebellar hemispheres suggest that the motor behavior of <i>M. tersillae</i> probably was less sophisticated than that exhibited by the extant rorqual and humpback species. The presence of an EQ value in this fossil species that is around 10 times higher than that of extant mysticetes opens new questions about brain evolution and provides new, invaluable information about the evolutionary path of morphological and size change in the brain of baleen whales.
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