Tyrannosaurus Slowed Growth During Lean Times
2020-01-07
The results of a detailed examination of bone cross-sections from immature tyrannosaurids have been published in the journal Science Advances.
In this study, thin cross-sections were taken from the leg fossils of two individuals and examined in detail. The traces of blood vessels can be used to estimate how much blood was carrying nutrients, and thus the bone's growth rate.
The bone cross-sections also preserve growth lines, which indicate the annual growth rate. These are like tree rings, resulting from different growth rates between warm seasons and winter. The study of two young individuals revealed that their growth rates differed. The paper suggests that "Tyrannosaurus could survive periods of food scarcity not by starving, but by slowing down its growth."
New Tyrannosaur Species Discovered in Canada, Named 'Reaper of Death'
2020-02-20
A fossil discovered in southern Alberta, Canada, in 2010 has been identified as a new species of tyrannosaur. After nearly a decade of storage at the Royal Tyrrell Museum of Palaeontology in Canada, a paper was published following a thorough investigation. A small jaw fragment was also found in another location in Alberta in 2018.
This dinosaur, estimated to be about 8 meters long, was named "Thanatotheristes degrootorum." The name is derived from Thanatos, the Greek god of death.
Thanatotheristes lived about 79.5 million years ago, a time when tyrannosaurs were beginning to dominate the ecosystem. As the fossil record consists only of parts of the skull, further research and discoveries are needed to understand the detailed ecology of Thanatotheristes.
Sauropod Rib Fossil Found in Amakusa (Kumamoto Prefecture)
2020-02-29
A rib fossil discovered in 1999 in the Early Cretaceous strata (about 100 million years old) of Goshoura Island, Amakusa City, Kumamoto Prefecture, has been identified as belonging to a large herbivorous sauropod dinosaur. Initially displayed at the Goshoura Cretaceous Museum as belonging to an ornithopod, investigation and cleaning from 2013 revealed it to be from a sauropod. The rib fossil is 42 cm long, 18 cm wide, and 0.9 cm thick. While the species has not been identified, the dinosaur is estimated to have been 15 meters in total length.
In Kyushu, sauropod fossils have been found in strata from about 130 million years ago in Kitakyushu City, and from about 80 million years ago in Amakusa City's Shimoshima Island and Satsumasendai City, Kagoshima Prefecture. This discovery helps fill the gap between these periods.
New Dinosaur Egg Species from a 55-Year-Old Fossil in Yamaguchi Prefecture
2020-03-16
A fossil collected in Shimonoseki City, Yamaguchi Prefecture, in September 1965 has been identified as a new species of dinosaur egg.
It was collected by a high school student at the time from the upper part of the Shimonoseki Subgroup of the Kanmon Group, from the Early Cretaceous period (about 120-100 million years ago). There are 12 egg fragments, with a thickness of 3.7 mm. The egg's diameter is estimated to be about 10 cm. Similar egg fossils have been discovered in Zhejiang Province, China, and Hwaseong City, Gyeonggi Province, South Korea, suggesting that the same species of dinosaur inhabited a wide area of East Asia.
The dinosaur that laid the egg has not been identified, but it was determined to be a new species based on slit-like cavities within the eggshell and its greater thickness compared to those from China. It has been given the scientific name "Multifissoolithus shimonosekiensis," meaning "split egg-stone from Shimonoseki."
The egg fossil was donated to Shimonoseki City in December 2019 (and is said to be housed at the Shimonoseki City Archaeological Museum).
Edmontosaurus and Ugrunaaluk are the Same Genus, Adapted to the Cold Arctic
2020-05-12
A study has shown that Edmontosaurus, which lived in North America between 53-40 degrees north latitude at the end of the Cretaceous (about 69 million years ago), and Ugrunaaluk, which lived in the Arctic region of northern Alaska, belong to the same genus.
The average temperature in the region where Ugrunaaluk lived (at a latitude of 80 degrees north during the late Cretaceous) is estimated to have been 6.2°C, and it is thought to have been a place covered in snow during the winter. Since Ugrunaaluk was described as a new species in 2015, some researchers had pointed out its similarity to the hadrosaurid Edmontosaurus. However, it was described as a new species due to some dissimilar features. A new comparative study by a team including Hokkaido University has concluded that "Edmontosaurus and Ugrunaaluk were of the same genus."
This announcement suggests that Edmontosaurus had adapted to the harsh Arctic environment and expanded its habitat.
Pre-hatch Tyrannosaurid Discovered
2020-10-25
A jaw fossil found in the Two Medicine Formation in Montana, USA, in 1983. A foot claw fossil found in the Horseshoe Canyon Formation in Alberta, Canada, in 2018. The importance of these fossils was not recognized when they were first discovered.
While a graduate student was studying the foot claw fossil, his supervisor showed him the small jaw fossil. Through 3D scanning and reconstruction, they determined that "both the foot claw and the jaw belonged to a tyrannosaurid."
The total length of the tyrannosaurid, estimated from the jaw fossil, is about 90 cm. It is believed to be a pre-hatch embryo. It already had a row of sharp, small teeth.
This discovery not only suggests the total length of this baby tyrannosaurid but also allows for an estimation of the egg size. The size of a tyrannosaurid egg is estimated to be 40 cm.
This discovery is said to provide clues for finding more tyrannosaurid eggs and hatchlings.