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Belemnites have been my core interest for decades, starting as an 8 year old kid when I saw and bought the pointy end of a large Cylindroteuthis in a curio shop (I still have it ). This led eventually to being able to research some Lower Jurassic ones for my Ph.D at university. I pursued another career after that (musical instrument repair and restoration) but palaeontology has remained a fairly fanatical interest ever since. Most of my early collection (including nearly all the research stuff) has been lost for various reasons but I've been able to replace much of it and added many new forms with field trips and purchases. So I'll start this thread with a few species from the Lower Lias, Lower Pliensbachian Stage, that first made me realise that not all belemnites look the same. This was a time of sudden diversity for the group. Earlier species (Sinemurian) are small and of low diversity, mostly belonging to the genus Nannobelus (= "dwarf dart"). (I'll do those later). All from the Charmouth Mudstone Formation, Stonebarrow Marl Member (formerly "Belemnite Marls"). Charmouth, Dorset, UK. Jamesoni Zone, Polymorphus Subzone. Bairstowius junceus/longissimus (Phillips, Miller). (junceus is the currently accepted name for the large form and longissimus for small, slender ones. The small ones appear to be immature individuals so they should probably all be longissimus which has priority.) A group all collected from the same small fallen block - almost certainly all the same species. (A large collection shows a complete series of intermediate forms, though probable sexual dimorphism divides fatter and thinner adults.) From the same beds - the scarce Coeloteuthis (Clastoteuthis) abrupta (Coeloteuthis is an awkward genus that needs revision - a bit complicated, but basically the original type specimen has been lost and the genus has ended up being based on a lectotype that is a different species and probably genus, and even family...) Just for comparison: "normal" belemnites - species of Passaloteuthis - exist in the same beds and are common. Here are two(?) species, the top two specimens probably being variants of one.
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I’m not sure if this has already been shared or not but a recent paper discussing the braincases of two Daspletosaurus specimens show more variation then previously thought. from the paper: “For sheer complexity, braincases are generally considered anatomically conservative. However, recent research on the braincases of tyrannosaurids have revealed extensive morphological variations. This line of inquiry has its root in Dale Russell’s review of tyrannosaurids in which he established Daspletosaurus torosus — a large tyrannosaurine from the Campanian of southern Alberta. In the wake of systematic revisions to tyrannosaurines previously assigned to Daspletosaurus, one potentially distinct species remains undescribed. This paper describes and compares a braincase referable to this species with that of the holotype for Daspletosaurus torosus using computerized-tomography-based reconstructions. The two braincases have numerous differences externally and internally. The specimen of Daspletosaurus sp. has a bottlenecked olfactory tract, short and vertical lagena, and a developed ascending column of the anterior tympanic recess. The holotype of Daspletosaurus torosus has many unusual traits, including an anteriorly positioned trochlear root, elongate common carotid canal, distinct chamber of the basisphenoid recess, asymmetry in the internal basipterygoid aperture, and laterally reduced but medially expanded subcondylar recess. This comparison also identified characters that potentially unite the two species of Daspletosaurus, including deep midbrain flexures in the endocasts. However, many character variations in the braincases are known in other tyrannosaurids to correlate with body size and maturity, or represent individual variations. Therefore, taxonomic and phylogenetic signals can be isolated from background variations in a more comprehensive approach by using additional specimens. New information on the two braincases of Daspletosaurus is consistent with the emerging view of tyrannosaurid braincases as highly variable, ontogenetically dynamic character complexes.” the paper: https://cdnsciencepub.com/doi/10.1139/cjes-2020-0185