How to recognize in situ fossil cephalopods: evidence from experiments with modern Nautilus

Field and flume experiments with modern Nautilus pompilius establish two prerequisites to recognize in situ preservation of fossil cephalopod shells (soft parts were within body chamber in situ at the time of fossilization): occurrence of the upper jaw within the body chamber and the position of jaws within the body chamber. Morphology of shells and jaws in modern and fossil nautiloids is so similar that these prerequisites can be applied for fossil nautiloids and provide implications for ammonoids. The upper jaws of Nautilus start to move at a water velocity of > 0.2 m/s, when the shells are reoriented with the aperture downstream; jaws are therefore unlikely to be secondarily deposited near the shell aperture by bottom currents. The lower jaws, moved at the velocity of > 0.1 m/s, can be deposited around the shell aperture by weak current (0.1–0.2 m/s in velocity), but never enter the inside of body chamber. Neither jaw is likely to be separately and selectively displaced from the inside of the body chamber through scavenging of the soft parts by burrowing infaunal animals. An upper jaw preserved inside the body chamber, together with a lower jaw, is thus a reliable indicator of in situ preservation; a sole lower jaw preserved around the shell aperture is likely to be secondarily deposited. Sedimentary structures inferring rapid burial events and jaw size are useful as additional evidence. Smaller jaws were more likely to be displaced from the body chamber by scavenging by infaunal animals after in situ burial, so that smaller jaws preserved within the body chamber suggest less scavenging. These findings are crucial to interpreting the taphonomic history and palaeo-ecology of fossil cephalopods.     

Experimental fragmentation patterns of modern Nautilus shells and the implications for fossil cephalopod taphonomy

Shells of modern Nautilus pompilius from the Philippines were experimentally fragmented designed to mimic: (1) transport with sediment; (2) sediment loading; and (3) collision during floating. The breaking patterns by other mechanisms (predation and implosion by hydrostatic pressure) documented in the literature were also considered. The breaking patterns produced by various mechanisms are distinct and can therefore be differentiated. The results allow identification of the distinct mechanisms responsible for specific fragmentation not only in modern Nautilus but also in fossil cephalopods. This is a new approach for the more complete recognition of post-mortem transport of fossil cephalopods and their early taphonomic history, and contributes to our understanding of their palaeobiogeography and palaeoecology.     

In Vitro Production of Lysine from 2,2'-Diaminopimelic Acid by Rumen Protozoa

Rumen protozoa can produce lysine from free 2,2'-diaminopimelic acid (DAP). However, the quantitative importance of this transformation has been disputed; lysine contents of protozoal incubation supernatants reported by Onodera & Kandatsu [12] and Masson & Ling [9] show a 26-fold difference. The in vitro experimental methods of both groups were compared to determine the causes of this difference. Lysine production was proportional to DAP concentration. Results with rumen protozoa from sheep or goats were similar. The incubation medium and deproteinizing procedure of the Welsh group gave a two-fold increase in lysine production compared with Japanese protocols. Omissions of rice starch from protozoal incubations slightly increased lysine production, whereas omissions of antibacterial agents resulted in varying, yet relatively small changes. The greatest cause of the difference was the number of rumen protozoa incubated. When this factor was taken into account, the difference in the maximum rates of lysine production between the Welsh and Japanese groups was only three-fold, namely 4.5 versus 15.0 nmol lysine/10⁵ protozoa/h. Adding other amino acids to the incubations suggested that DAP uptake by rumen protozoa may occur via transport system ASC. The importance of DAP metabolism by protozoa as a source of lysine for ruminant host animals is discussed.     

Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido,Japan: implication for planktic duration at early ontogenetic stage

Tajika, A. & Wani, R. 2011: Intraspecific variation of hatchling size in Late Cretaceous ammonoids from Hokkaido, Japan: implication for planktic duration at early ontogenetic stage. Lethaia, Vol. 44, pp. 287–298. Intraspecific variations of the early shell dimensions (ammonitella and protoconch diameters) of two Late Cretaceous (earliest Campanian) ammonoid species (Gaudryceras tenuiliratum and Hypophylloceras subramosum) from the Haboro and Ikushumbetsu areas, Hokkaido, Japan, show no significant difference between these areas that are approximately 110 km apart. The geographic distributions of G. tenuiliratum and H. subramosum are supposed to be mainly controlled by the flotation and transportation during the embryonic stage within floating egg masses and/or post‐embryonic stage because of their small hatchling sizes (1.18–1.46 mm in diameter for G. tenuiliratum, and 0.91–1.13 mm in diameter for H. subramosum), suggesting these two ammonite species at the embryonic and/or post‐embryonic stages were transported at least 110 km. Postulating that the velocity of palaeocurrent around the Haboro and Ikushumbetsu areas during the Cretaceous Period was 0.25 m/s, similar to those in the modern ocean current flowing off the eastern Pacific coast of Hokkaido, the egg masses and/or hatchlings of G. tenuiliratum and H. subramosum were buoyant and transported more than 5 days. The preliminary comparison of hatchling size through time suggests that the hatching sizes of H. subramosum in Hokkaido increased slightly from the Middle Turonian until the earliest Campanian (during about 7 Myr). □ammonoid, hatchling, paleoecology, variation, Cretaceous.     

Formation of 2-Aminobutanoic Acid from Threonine and Methionine by Mixed Rumen Ciliate Protozoa

Precursors of 2-aminobutanoic acid (2-ABA), found in the incubation medium of mixed rumen ciliate protozoa, were examined with washed or starved bacteria-free ciliates. Threonine and methionine strongly stimulated the formation of 2-ABA. Formation of 2-ABA by direct conversion of threonine and dethiomethylation of methionine was confirmed by radiotracer experiments with [U-¹⁴C]L-threonine and [carboxyl-¹⁴C] and [methyl-¹⁴C]L-methionine.     

Isotricha jalaludinii N. Sp. Found from the Rumen of Lesser Mouse Deer, Tragulus javanicus, in Malaysia

Isotricha jalaludinii n. sp. found in the rumen of lesser mouse deer, Tragulus javanicus, in Malaysia was described and illustrated. This new species is characterized by the location and direction of the vestibulum, shape of the macronucleus, and absence of a dent at the vestibular opening. The presence of single peculiar isotrichid species in the rumen of mouse deer, which is recognized as one of the most primitive ruminants, suggests that the isotrichid ciliates similar to I. jalaludinii and Isotricha intestinalis were established at a fairly early period during the evolution of ruminants.