Category Archives: News

Rugosodon, earliest multituberculate mammal from Jurassic of China

A new paper in Science, describing Rugosodon. The Supplementary Materials are free.

Chong-Xi Yuan, Qiang Ji, Qing-Jin Meng, Alan R. Tabrum & Zhe-Xi Luo
(2013) Earliest Evolution of Multituberculate Mammals Revealed by a
New Jurassic Fossil Science 341 (6147): 779-783
DOI: 10.1126/science.1237970
http://www.sciencemag.org/content/341/6147/779

Multituberculates were successful herbivorous mammals and were more diverse and numerically abundant than any other mammal groups in Mesozoic ecosystems. The clade also developed diverse locomotor adaptations in the Cretaceous and Paleogene. We report a new fossil skeleton from the Late Jurassic of China that belongs to the basalmost multituberculate family. Dental features of this new Jurassic multituberculate show omnivorous adaptation, and its well-preserved skeleton sheds light on ancestral skeletal features of all multituberculates, especially the highly mobile joints of the ankle, crucial for later evolutionary success of multituberculates in the Cretaceous and Paleogene.

Lots of news stories:

http://www.nature.com/news/fossil-reveals-features-of-mammal-line-that-outlived-dinosaurs-1.13568

http://news.nationalgeographic.com/news/2013/08/130815-multituberculate-rugosodon-early-mammal-evolution/

http://www.livescience.com/38924-ancient-rodentlike-creature-discovered.html

 

Mid Jurassic Mystery Mammal Solved – Or Not!

You wait since 1997 for another haramiyid to come along, then you get two in the same issue of Nature!:

A new arboreal haramiyid shows the diversity of crown mammals in the Jurassic period

Xiaoting Zheng, Shundong Bi, Xiaoli Wang & Jin Meng

Nature, Vol. 500, No. 7461. (8 August 2013), pp. 199-202,

doi:10.1038/nature12353

http://www.nature.com/nature/journal/v500/n7461/full/nature12353.html

A major unsolved problem in mammalian evolution is the origin of Allotheria, including Multituberculata and Haramiyida1–5. Multituber- culates are the most diverse and best known Mesozoic era mammals and ecologically resemble rodents, but haramiyids are known mainly from isolated teeth, hampering our search for their phylogenetic relationships. Here we report a new haramiyid from the Jurassic period of China, which is, to our knowledge the largest reported so far. It has a novel dentition, a mandible resembling advanced multi- tuberculates and postcranial features adapted for arboreal life. Our phylogenetic analysis places Haramiyida within crown Mammalia, suggesting the origin of crown Mammalia in the Late Triassic period and diversification in the Jurassic, which contrasts other estimated divergence times of crown Mammalia6–8. The new haramiyid reveals additional mammalian features of the group, helps to identify other haramiyids represented by isolated teeth, and shows again that, regardless of various phylogenetic scenarios, a complex pattern of evolution involving many convergences and/or reversals existed in Mesozoic mammals.

– Ian

Another Mid Jurassic Mystery Mammal Solved!

A Jurassic mammaliaform and the earliest mammalian evolutionary adaptations

Chang-Fu Zhou, Shaoyuan Wu, Thomas Martin & Zhe-Xi Luo

–Nature: Vol. 500, #7461, pp. 163-167 [doi: 10.1038/nature12429]

http://www.nature.com/nature/journal/v500/n7461/full/nature12429.html

The earliest evolution of mammals and origins of mammalian features can be traced to the mammaliaforms of the Triassic and Jurassic periods that are extinct relatives to living mammals. Here we describe a new fossil from the Middle Jurassic that has a mandibular middle ear, a gradational transition of thoracolumbar vertebrae and primitive ankle features, but highly derived molars with a high crown and multiple roots that are partially fused. The upper molars have longitudinal cusp rows that occlude alternately with those of the lower molars. This specialization for masticating plants indicates that herbivory evolved among mammaliaforms, before the rise of crown mammals. The new species shares the distinctive dental features of the eleutherodontid clade, previously represented only by isolated teeth despite its extensive geographic distribution during the Jurassic.  This eleutherodontid was terrestrial and had ambulatory gaits, analogous to extant terrestrial mammals such as armadillos or rock hyrax. Its fur corroborates that mammalian integument had originated well before the common ancestor of living mammals.

– Ian

 

Giant lizard named for Jim Morrison tells tale of climate change

Giant lizards occupied herbivorous mammalian ecospace during the Paleogene greenhouse in Southeast Asia
Jason J. Head, Gregg F. Gunnell, Patricia A. Holroyd, J. Howard Hutchison and Russell L. Ciochon

http://rspb.royalsocietypublishing.org/content/280/1763/20130665

and some press
http://www.nature.com/nature/journal/v498/n7453/full/498141d.html?WT.ec_id=NATURE-20130613
http://edition.cnn.com/2013/06/05/us/climate-change-jim-morrison-lizard/index.html

– Jacqueline

Evolutionary origin of turtle shell

Tyler R. Lyson, Gabe S. Bever, Torsten M. Scheyer, Allison Y. Hsiang & Jacques

A. Gauthier (2013) Evolutionary Origin of the Turtle Shell.
Current Biology (advance online publication)
doi: http://dx.doi.org/10.1016/j.cub.2013.05.003
http://www.sciencedirect.com/science/article/pii/S0960982213005666

The origin of the turtle shell has perplexed biologists for more than two
centuries. It was not until Odontochelys semitestacea was discovered,
however, that the fossil and developmental data could be synthesized into
a model of shell assembly that makes predictions for the as-yet
unestablished history of the turtle stem group. We build on this model by
integrating novel data for Eunotosaurus africanus-a Late Guadalupian
(~260 mya) Permian reptile inferred to be an early stem turtle. Eunotosaurus
expresses a number of relevant characters, including a reduced number of
elongate trunk vertebrae (nine), nine pairs of T-shaped ribs, inferred loss of
intercostal muscles, reorganization of respiratory muscles to the ventral side
of the ribs, (sub)dermal outgrowth of bone from the developing perichondral
collar of the ribs, and paired gastralia that lack both lateral and median elements.
These features conform to the predicted sequence of character acquisition
and provide further support that E. africanus, O. semitestacea, and
Proganochelys quenstedti represent successive divergences from the turtle
stem lineage. The initial transformations of the model thus occurred by the Middle
Permian, which is congruent with molecular-based divergence estimates for the
lineage, and remain viable whether turtles originated inside or outside crown Diapsida.