Evolution of Jurassic Marine Reptiles

The long-term ecology and evolution of marine reptiles in a Jurassic seaway

 

Marine reptiles flourished in the Mesozoic oceans, filling ecological roles today dominated by crocodylians, large fish, sharks and cetaceans. Many groups of these reptiles coexisted for over 50 million years (Myr), through major environmental changes. However, little is known about how the structure of their ecosystems or their ecologies changed over millions of years. We use the most common marine reptile fossils—teeth—to establish a quantitative system that assigns species to dietary guilds and then track the evolution of these guilds over the roughly 18-million-year history of a single seaway, the Jurassic Sub-Boreal Seaway of the United Kingdom. Groups did not significantly overlap in guild space, indicating that dietary niche partitioning enabled many species to live together. Although a highly diverse fauna was present throughout the history of the seaway, fish and squid eaters with piercing teeth declined over time while hard-object and large-prey specialists diversified, in concert with rising sea levels. High niche partitioning and spatial variation in dietary ecology related to sea depth also characterize modern marine tetrapod faunas, indicating a conserved ecological structure of the world’s oceans that has persisted for over 150 Myr.

Image credit: Nikolay Zverkov.

Ref & abstract credit :https://www.nature.com/articles/s41559-018-0656-6

 

Caihong juji - newly discovered Jurassic theropod

The newly discovered Jurassic theropod Caihong juji, had a beautiful iridescent coloration .
This new theropod shows an array of bony features, as well as plumage characteristics and putative melanosome morphologies not previously seen in other Paraves, and thus further informs the pattern of character acquisition close to the origin of avian flight.

The Jurassic Yanliao theropods have offered rare glimpses of the early paravian evolution and particularly of bird origins, but, with the exception of the bizarre scansoriopterygids, they have shown similar skeletal and integumentary morphologies. Here we report a distinctive new Yanliao theropod species bearing prominent lacrimal crests, bony ornaments previously known from more basal theropods. It shows longer arm and leg feathers than Anchiornis and tail feathers with asymmetrical vanes forming a tail surface area even larger than that in Archaeopteryx. Nanostructures, interpreted as melanosomes, are morphologically similar to organized, platelet-shaped organelles that produce bright iridescent colours in extant birds. The new species indicates the presence of bony ornaments, feather colour and flight-related features consistent with proposed rapid character evolution and significant diversity in signalling and locomotor strategies near bird origins.

Image credit: Velizar Simeonovski, Field Museum.
Ref  & abstract credit :https://www.nature.com/articles/s41467-017-02515-y

ജുറാസിക് കാലഘട്ടത്തിലെ ഈന്ത് ചെടികള്‍ ഇന്ത്യയിൽ കണ്ടെത്തി

ജുറാസിക് കാലഘട്ടത്തില്‍ ഭൂമിയിലുണ്ടായിരുന്ന ഈന്ത് വര്‍ഗത്തില്‍പ്പെട്ട രണ്ട് ചെടികളെ ഗവേഷകര്‍ ഒഡിഷയില്‍ കണ്ടെത്തി. ജീവിക്കുന്ന ഫോസില്‍ എന്നാണ് സൈക്കാസ് (ഈന്ത്) കുടുംബത്തിലെ ചെടികള്‍ വിശേഷിപ്പിക്കപ്പെടുന്നത്.

സൈക്കാസ് ഒറിക്‌സന്‍സിസ്, സൈക്കാസ് നയാഗാര്‍ഹന്‍സിസ് എന്നിങ്ങനെയാണ് കണ്ടെത്തിയ ചെടികളുടെ ശാസ്ത്രീയനാമം. 

ഭൂമിയില്‍ 20 കോടി വര്‍ഷങ്ങള്‍ക്ക് മുമ്പാണ് ദിനോസറുകള്‍ അടക്കിവാണ ജുറാസിക് കാലഘട്ടം നിലനിന്നിരുന്നത്. നീണ്ട ഇലകളുള്ള സൈക്കാസ് വിഭാഗത്തിലെ ചെടികള്‍ ഈ കാലഘട്ടത്തില്‍ സുലഭമായിരുന്നു. ജുറാസിക് യുഗത്തില്‍ നിലനിന്നിരുന്ന ചുരുക്കം സസ്യവര്‍ഗങ്ങളാണ് ഇന്ന് ഭൂമിയില്‍ അവശേഷിക്കുന്നത്.  

Indian scientists  have discovered two new Cycads species of plants in Odisha which were dominant some 201 million to 145 million years ago, popularly known as the Jurassic period. 

Cycads are considered to be an ancient group of seed plants which have crown of large compound leaves and a stout trunk. They are regarded as living fossils.
Cycas is the type genus and the only genus recognised in the family Cycadaceae.

The discovery of the two new species was published in July issue of Asian Journal of Conservation Biology.
IANS

Qijianglong guokr

A team of paleontologists from Japan, China and Canada has described a new genus and species of sauropod dinosaur that lived during the Upper Jurassic epoch, approximately 160 million years ago.

The new dinosaur, named Qijianglong guokr (means Dragon of Qijiang), belongs to Mamenchisauridae, a family of dinosaurs known for their extremely long necks sometimes measuring up to half the length of their bodies.
The neck vertebrae and the head of the dinosaur were found near Qijiang, Chongqing Municipality, southern China.
“It is rare to find a head and neck of a long-necked dinosaur together because the head is so small and easily detached after the animal dies,” said Tetsuto Miyashita, a PhD student at the University of Alberta and a co-author of the paper published in the Journal of Vertebrate Paleontology.
Qijianglong guokr was about 15 meters in length. It had neck vertebrae that were filled with air, making the neck relatively lightweight despite its enormous size.
Interlocking joints between the vertebrae also indicate a surprisingly stiff neck that was much more mobile bending vertically than sideways, similar to a construction crane.
“Qijianglong guokr is a cool animal. If you imagine a big animal that is half-neck, you can see that evolution can do quite extraordinary things,” Miyashita said.
Mamenchisaurids are only found in Asia, but the discovery of Qijianglong guokr reveals that there could be as many differences among mamenchisaurids as there are between long-necked dinosaurs from different continents.
“Qijianglong guokr shows that long-necked dinosaurs diversified in unique ways in Asia during Jurassic times – something very special was going on in that continent. Nowhere else we can find dinosaurs with longer necks than those in China. The new dinosaur tells us that these extreme species thrived in isolation from the rest of the world,” Miyashita said.
“Mamenchisaurids evolved into many different forms when other long-necked dinosaurs went extinct in Asia. It is still a mystery why mamenchisaurids did not migrate to other continents.”
It is possible that the dinosaurs were once isolated as a result of a large barrier such as a sea, and lost in competition with invading species when the land connection was restored later.
The skeleton of Qijianglong guokr is now housed in a local museum in Qijiang.

Reference :
Lida Xing et al. A new sauropod dinosaur from the Late Jurassic of China and the diversity, distribution, and relationships of mamenchisaurids. Journal of Vertebrate Paleontology, published online: January 26, 2015; doi: 10.1080/02724634.2014.889701