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New Discoveries of Fossil Mammals
Filling in the blanks


 Earliest Elephant Ancestor Announced
 July, 2009



 

Eritherium azzouzorum, the earliest Proboscidean



Earliest Elephant

Discovery of Elephants' Oldest Know Relative
ScienceDaily (July 30, 2009)

Emmanuel Gheerbrant, paleontologist at the Paris Museum, discovered one of the oldest modern ungulates related to the elephant order. The beginnings of the radiation (diversification) of the modern mammals (placental orders) remain poorly known because of fossil gaps, and especially in some key Southern continents such as Africa. Emmanuel Gheerbrant, researcher at the CNRS, reports the discovery of one of the oldest known modern ungulates in Paleocene beds from Morocco. Dated to about 60 millions years ago, this fossil mammal belongs to a new species called Eritherium azzouzorum. It comes from the same Ouled Abdoun phosphate basin which yielded Phosphatherium escuilliei, which was until the Eritherium's discovery the oldest and most primitive proboscidean found. This is the oldest known African ungulate (called paenungulates), and among them the oldest known member of the elephant order (proboscideans).

Eritherium azzouzorum is small (4 to 5 kg) and extraordinarily primitive. It exemplifies the emergence of a modern order of ungulates at a very primitive stage, which is illustrated by a likeness among proboscideans within primitive groups such as some condylarths (louisinines, extinct) and non-paenungulate afrotherians (elephant shrews, Eocene to Present). Its primitiveness indicates the rapid evolution of the proboscideans at the aleocene-Eocene transition (e.g., with increasing size), and the rapid radiation of the African ungulates after the Cretaceous-Tertiary crisis (65 millions years ago), probably in relation to the colonization of the herbivorous African free niches.

Eritherium is a new major find, and one of the oldest known calibration point of the phylogeny of the placental orders. It is especially important for the fine tuning of the placental molecular trees.
Source

More on Eritherium:

WORLDAREA.INFO (June 30, 2009)

Scientists have found the fossil of a 60-million-year-old creature in Morocco, which is the rabbit sized ancestor of the modern day elephant. Paleontologist Emmanuel Gheerbrant discovered the rabbit-size proto-elephant’s skull fragments in a basin 60 miles (100 kilometers) east of Casablanca, Morocco. The creature, called Eritherium azzouzorum, bolsters the case that whole new orders of mammals were already around less than 6 million years after global catastrophe ended the age of reptiles some 65.5 million years ago. Elephant ancestors now join the likes of rodents and early primates as some of the first known mammals to walk the Earth during the Paleocene era, 65.5 to 55 million years ago (prehistoric time line), according to Gheerbrant. “Much of the story of the newly discovered creature can be found in its teeth,” said Gheerbrant, of the National Museum of Natural History in Paris. Two of the creature’s lower front teeth jut a fraction of an inch out from its jaw. No other fossils of the time have teeth like this. “This is some kind of precursor of the tusk of the more modern (elephant),” Gheerbrant said. Based on the skull fragments, Gheerbrant guessed that the proto-elephant was probably no more than 20 inches (50 centimeters), tip to tail— “something like a very large rabbit,” size wise. Because the find consists of skull and jaw fragments only, Gheerbrant said there’s not enough evidence to know what it looked like— or whether it had anything resembling a trunk or elephantine ears. Sixty million years ago, Africa was lush with vegetation and disconnected from the Eurasian continent to the north. The continent was an evolutionary hotbed, Gheerbrant said. “The rise of elephant-like mammals hot on dinosaurs’ heels suggests there are many more mammals from the period to be found,” he said. “More fossil hunts are needed to uncover how evolution put mammals center stage once the reptilian resource hogs had gone,” he added.

Source





 A Review and Update of the Hobbit Controversy
 December, 2007



 

Homo floresiensis Skull LB1. Illustration courtesy Talk Origins

The Homo floresiensis Controversy

Collin Groves, Hayati Jorunal of Biosciences, December, 2007, p.123-126


Abstract:  A completely new and unexpected quasi human species, Homo floresiensis, nicknamed the Hobbit, was described in 2004 from Liang Bua, a cave in Flores. Like many important new contributions to the human fossil record in the past, many commentators refused to believe that a new species had been discovered, and the type specimen was interpreted as a pathological modern human, usually as a microcephalic dwarf. There is no substance to these claims: close analysis shows that Homo floresiensis is not only a genuinely new species, but that its closest affinities lie with Plio-Pleistocene African species such as Homo habilis, so that it documents an earlier dispersal of hominins from Africa and had hitherto been suspected.
pdf version of the paper in its entirety

***********************************************************************
 Creationist views on Homo floresiensis: (Assembled by TalkOrigins)

Soggy Dwarf Bones, by Carl Wieland (Answers in Genesis)
Hobbling the Hobbit?, by Carl Wieland (Answers in Genesis)
Creationism May Explain Skeletal Remains Better Than Darwinism, by Mary Rettig (Agape Press)
Erroding Evolution's believability, by Kelly Hollowell (WorldNetDaily)
Hobbit Heresy, by Brad Harrub and Bert Thompson
Note: The Institute for Creation Research had published an article, "Yet another "rethinking" of "human evolution". That article has been removed from their website, and in fact, the ICR now has no mention anywhere of Homo floresiensis.


 New fossil armored mammal from the high peaks
 of Chile
 December, 2007



 
Parapropalaehoplophorus septentrionalis illustrations courtesy Society of Vertebrate Paleontology.

A New Basal Glyptodontid and Other Xenarthra of the Early Miocene Chucal Fauna, Northerm Chile.

Darin A. Croft, John J. Flynn and André Wyss, Journal of Vertebrate Paleontology, Volume 27:781-797.


The only reason that most people ascend to 14,000 feet is to go skiing. For a group of U. S. and Chilean scientists, however, such altitudes are ideal fossil-hunting terrain. In fact, over the past 10 years their explorations have taken them to one of the highest elevation vertebrate fossil sites in the world. The localities near Salar de Surire in northern Chile have yielded several hundred fossil mammal specimens. A study led by Dr. Darin Croft of Case Western Reserve University has determined that one of these specimens, a partial skeleton collected in 2004, represents a new species of armored mammal known as a glyptodont, which they have named Parapropalaehoplophorus septentrionalis. As Dr. Croft says, “The name of this new species is a mouthful, but it does roll off the tongue nicely!” The discovery is reported in the December issue of the Journal of Vertebrate Paleontology.

Glyptodonts are a group of now-extinct armored mammals most closely related to modern armadillos. Unlike armadillos, glyptodonts had shells made of mostly immovable plates and reached much larger sizes; some of the largest likely weighed two tons – the size of a small car! The new species, P. septentrionalis, is much smaller, weighing a mere 200 pounds and it documents the early history of this interesting group, which went extinct at about the same time that humans arrived in the New World. “When we collected this fossil, we had no idea that it would turn out to be a new species,” said Croft. “We knew that it would be an important specimen, given its completeness, but it was only after careful comparison to other known species that we realized how unusual it was."

The new species of glyptodont is one of about 18 mammal species known from the Chucal Fauna, the collective name given to the fossils from the Salar de Surire region. Other Chucal mammals include armadillos, marsupials (opossum relatives), rodents, and a variety of extinct hoofed mammals. These mammals, along with plant fossils recovered from the same area, suggest that northern Chile had relatively few trees 18 million years ago. John Flynn, a co-author of the study said that " Our sites are now located more than 14,500 feet above sea level, but when these animals were alive the region was at much lower elevations. That means that the Chucal fossils give us a unique insight into the timing and rate of uplift of the high Andes.”

Croft said that “working in the Altiplano of Chile can be challenging; the air is thin, water is scarce, and the temperatures plummet as soon as night falls. On the other hand, there are hardly any bugs, you don't have to worry much about rain, and the stars are spectacular.”

Source: Society of Vertebrate Paleontology Press Release



 Yanoconodon allini sheds new light on the
 evolution of the mammalian ear.
 March 15, 2007



 
Yanoconodon illustrations courtesy Nature.

A new eutriconodont mammal and evolutionary development in early mammals.

Luo Z-X (1,2), Chen P. (3), Li G. (3) and Chen M. (2), (2007) Nature 446:288-293.

Abstract: Detachment of the three tiny middle ear bones from the reptilian mandible is an important innovation of modern mammals. Here we describe a Mesozoic eutriconodont nested within crown mammals that clearly illustrates this transition: the middle ear bones are connected to the mandible via an ossified Meckel's cartilage. The connected ear and jaw structure is similar to the embryonic pattern in modern monotremes (egg-laying mammals) and placental mammals, but is a paedomorphic feature retained in the adult, unlike in monotreme and placental adults. This suggests that reversal to (or retention of) this premammalian ancestral condition is correlated with different developmental timing (heterochrony) in eutriconodonts. This new eutriconodont adds to the evidence of homoplasy of vertebral characters in the thoraco-lumbar transition and unfused lumbar ribs among early mammals. This is similar to the effect of homeobox gene patterning of vertebrae in modern mammals, making it plausible to extrapolate the effects of Hox gene patterning to account for homoplastic evolution of vertebral characters in early mammals.

Published in Nature

Here we have even more evidence, in the form of another transitional stage, for the evolution of mammals from their reptilian ancestors.

 Homo floresiensis not a microcephalic: valid new species
 February 2, 2007



  Homo floresiensis compared with a modern human skull.

Brain shape in human microcephalics and Homo floresiensis



Dean Falk, Charles Hildebolt, Kirk Smith, M. J. Morwood, Thomas Sutikna, Jatmiko, E. Wayhu Saptomo, Herwig Imhof, Horst Seidler, and Fred Prior

Edited by Marcus E. Raichle, Washington University School of Medicine, St. Louis, MO, and approved December 7, 2006 (received for review October 18, 2006)

Abstract: Because the cranial capacity of LB1 (Homo floresiensis) is only 417 cm3, some workers propose that it represents a microcephalic Homo sapiens rather than a new species. This hypothesis is difficult to assess, however, without a clear understanding of how brain shape of microcephalics compares with that of normal humans. We compare three-dimensional computed tomographic reconstructions of the internal braincases (virtual endocasts that reproduce details of external brain morphology, including cranial capacities and shape) from a sample of 9 microcephalic humans and 10 normal humans. Discriminant and canonical analyses are used to identify two variables that classify normal and microcephalic humans with 100% success. The classification functions classify the virtual endocast from LB1 with normal humans rather than microcephalics. On the other hand, our classification functions classify a pathological H. sapiens specimen that, like LB1, represents an 3-foot-tall adult female and an adult Basuto microcephalic woman that is alleged to have an endocast similar to LB1's with the microcephalic humans. Although microcephaly is genetically and clinically variable, virtual endocasts from our highly heterogeneous sample share similarities in protruding and proportionately large cerebella and relatively narrow, flattened orbital surfaces compared with normal humans. These findings have relevance for hypotheses regarding the genetic substrates of hominin brain evolution and may have medical diagnostic value. Despite LB1's having brain shape features that sort it with normal humans rather than microcephalics, other shape features and its small brain size are consistent with its assignment to a separate species.

Published in the Proceedings of the National Academy of Science

 Earliest Known Gliding Mammal,Volaticotherium antiqus
 Announced December 13, 2006

  Image courtesy National Geographic  
Image courtesy Pharyngula

"Gliding flight has independently evolved many times in vertebrates. Direct evidence of gliding is rare in fossil records and is unknown in mammals from the Mesozoic era. Here we report a new Mesozoic mammal from Inner Mongolia, China, that represents a previously unknown group characterized by a highly specialized insectivorous dentition and a sizable patagium (flying membrane) for gliding flight. The patagium is covered with dense hair and supported by an elongated tail and limbs; the latter also bear many features adapted for arboreal life. This discovery extends the earliest record of gliding flight for mammals to at least 70 million years earlier in geological history, and demonstrates that early mammals were diverse in their locomotor strategies and lifestyles; they had experimented with an aerial habit at about the same time as, if not earlier than, when birds endeavoured to exploit the sky." (Nature 444, 889-893 (14 December 2006)
Volaticotherium antiqus – Volatico, Latin for “gliding”; therium, Latin for “beast” and antiqus– Latin for ancient.


 Ancient Mammal from New Zealand,
 Announced December 11, 2006

   
Images from PNAS

Scientists lead by Trevor Worthy announced the discovery of the first fossil terrestrial mammal from New Zealand. Phylogenetic analysis of the material, so far limited to two jaws and part of a femur, indicate that the animal was related to very primitive mammals before the splitting off of monotremes and eutherians. The fossil dates to the Miocene, between 16 and 19 million years ago. The closest known relatives lived around 135 million years ago. The New Zealand fossils represent the last surviving member of a "ghost lineage" thought to have been long extinct.
The resaerch was published in the Proceedings of the National Academy of Science.

 First new fossil mammal from the Philippines in 50  years,
 Bubalus cebuensis announced October, 2006
Foot bones — Left metatarsals (foot bones) of Bubalus bubalis (or domestic water buffalo), Bubalus mindorensis (or tamaraw, a dwarf buffalo species that lives today on Mindoro Island in the Philippines) and Bubalus cebuensis (the new species of extinct dwarf buffalo identified by John J. Flynn of the American Museum of Natural History and colleagues at The Field Museum and Case Western Reserve University).
Credit: John Weinstein, The Field Museum  
A joint U.S. and Philippine research group, including American Museum of Natural History paleontologist John J. Flynn, has identified a new species of miniature buffalo from fossil remains found on Cebu Island in the Philippines. The extinct dwarf buffalo, named Bubalus cebuensis, is distinctive in its proportions and small size, estimated to stand only 2.5 feet tall at the shoulder and to weigh about 350 pounds (contemporary water buffalos stand six feet tall and can weigh up to 2,000 pounds). A different species of dwarf buffalo, Bubalus mindorensis (or tamaraw), lives today on Mindoro Island in the Philippines, but even this animal, which stands three feet tall and weighs close to 500 pounds, is large compared to B. cebuensis. It has not been possible to precisely date the fossil but it is unlikely to be more than a few tens of thousands of years old—from either the Pleistocene or Holocene Epochs. Fossils are quite rare in the tropical environments of the Philippines, and this is the first fossil mammal of any age to be reported from Cebu Island. The fossil remains were found 50 years ago in a phosphate mine by engineer Michael Armas. He kept them safe for nearly four decades and then showed them to physician Hamilcar Intengan, who recognized their importance and brought them to The Field Museum for identification and study in 1995.
Source of story: AMNH.



 Tusks Record Savage Yearly Battles Between Bull Mastodons
 announced October, 2006
Oct. 19, 2006 —Battle scars on male mastodon tusks reveal that the Ice Age giants fought in brutal combat each year during seasonal phases of heightened sexual activity and aggression, according to new findings that will be announced at this week's Society of Vertebrate Paleontology meeting in Ontario.

The discovery counters the view that now-extinct mastodons were peaceful, passive creatures that rarely engaged in battles. It also strengthens the link between mastodon and modern elephant behavior, since male bull elephants also fight seasonal, hormonally-charged battles to show their dominance and win desired mates. Like warriors with different weapons, however, the two animals had distinct fighting techniques, lead author Daniel Fisher, a University of Michigan paleontologist, told Discovery News.

"Mastodon tusks curve upward strongly at the tips and appear to have been used in a vigorous up-thrusting motion," explained Fisher, who added that elephant tusks are less curved and therefore tend to be used more "in a straight thrusting move." Fisher's analysis of mastodon tusks and skulls revealed that such ramming caused the lower part of the tusk to rotate backward, "crunching it against the back wall of the tusk socket." He found that although the tusk continued to grow by adding layers of ivory to its base, pitted scars line up along the outside curve of the tusk base. "It's not just one event, but a whole series of events that is preserved in this tusk record of fighting," he said.

Using previous research about mastodon tusk growth patterns, Fisher also found the scars correspond to seasonal patterns — the pits formed each year of the adult male animal's life during mid-spring to early summer. Studies on mastodon vertebrae also helped fill out a picture of gory battles between the 8 to 10-foot-tall creatures. "For example, we have evidence of tusks stabbing into the vertebral column, penetrating the space traversed by the spinal cord, from a direction that implies the victim was already lying on his side on the ground; in other words, the violence went on, even after one animal was down," Fisher said. Other fossils suggest some of the animals were butchered in autumn — likely by humans, who may have caused or contributed to the extinction of mastodons 11,000 years ago.

Jeffrey Saunders, curator and chair of geology at the Illinois State Museum, told Discovery News that he has excavated over 72 mastodons. "I always viewed them as being rather passive animals because I never found many broken bones — maybe one or two broken ribs — but I greatly respect Dr. Fisher's work and I continue to be open-minded about the possibilities," he said. Saunders, who once found himself between two fighting bull male elephants while in a small jeep, added, "I also think it's interesting that similarities between mastodons and modern elephants seem to persist, given that these animals parted evolutionary ways 40 million years ago. The basic elephant design must be successful to have persisted so long."


Source of story: AMNH.



 New species of notoungulate, Hemihegetotherium trilobus
 from Bolivia announced September 19, 2006

  Courtesy National Geographic

Fossil Mammal Resembling Dog-Hare Hybrid Found in Bolivia
Nicholas Bakalar
for National Geographic News
September 19, 2006
In paleontology, not all big finds happen out in the field. A new species of ancient mammal has been discovered—in the fossil collection of the National Museum of Natural History in La Paz, Bolivia. The animal, which has been assigned the tongue-twisting name Hemihegetotherium trilobus, is a member of an extinct group called notoungulates, a term that means "southern hoofed mammals." The creature resembles a cross between a dog and a hare. It was about the size of a beagle, weighing between 20 and 25 pounds (9 and 11 kilograms), and probably looked something like a capybara, the largest modern-day rodent. Specimens of the creature's bones—including almost complete skulls and jaws and parts of the skeleton—have been in collections in various museums for more than 30 years. "Normally, you think of finding these in the field," said Darin A. Croft, an assistant professor of anatomy at the Case Western Reserve University School of Medicine in Cleveland, Ohio. "But for this animal, no one who specialized on this group had taken a close look. No one had had the time or the expertise to look at the detailed anatomy." Croft found the bones in a sample drawer while visiting the museum during a 1999 paleontology conference in Bolivia. He noticed at the time that the molars had three lobes, whereas other notoungulates' teeth had only two, so he decided to study the remains further. Croft and colleagues describe their findings in the June issue of the Journal of Vertebrate Paleontology. Source: National Geographic Online


 Early mammals may have been venomous:
 2006 paper documents early distribution of tarsal spurs

Left, Tarsal spur of Platypus.             Center, Distribution of tarsal spurs in mammalia;         Right, Ankle region of Zhangheotherium
"The extratarsal spur in extant monotremes consists of an os calcaris and a cornu calcaris. A poisonous extratarsal spur oc- curs only in the platypus (Ornithorhynchus); a possibly secondarily non-poisonous spur is present in echidnas (Tachy- glossus and Zaglossus). Some therian mammals (e.g., bats), reptiles (Chamaeleo), and amphibians have a spur-like struc- ture in the ankle, but this is not homologous to the extratarsal spur of monotremes. Among fossilmammals, the co-ossified os calcaris and ossified cornu calcaris have been found in the eutriconodontan Gobiconodon and in the spalacotheroid “symmetrodontan” Zhangheotherium. Here we describe the os calcaris in several multituberculate mammals from the Late Cretaceous of the Gobi Desert, Mongolia. The multituberculate os calcaris is a large, flat bone, generally similar to that in males of the extant monotreme species, but the cornu calcaris is not ossified. In Gobiconodon and Zhangheotherium the os- sified cornu calcaris is fused to the os calcaris probably to provide the bony support for the keratinous spur. We hypothesize that the os calcaris in these Mesozoic mammal groups is homologous to that of monotremes. However, the extratarsal spur has not been found in non-mammalian cynodonts nor in other synapsids. A platypus-like os calcaris might be an apomorphic characteristic of basal Mesozoic mammals and is secondarily lost in crown therians; the os calcaris is con- firmed to be absent in well-preserved tarsal structures of the earliest known crown therian mammals. We speculate that the os calcaris, the cornu calcaris, and its associated venom gland might have served the function of a defensive structure dur- ing the “dark ages” of mammalian history, when dinosaurs ruled the Earth. This structure is a plesiomorphic character retained in extant monotremes and cannot be used as an autapomorphy of Monotremata."

(Hurum, J.H., Luo, Z-X., and Kielan-Jaworowska, Z. 2006. Were mammals originally venomous? Acta Palaeontologica Polonica 51 (1): 1–11.) (pdf version)




  Discovery of Castorocauda lutrasimilis announced in
  Februray, 2006

 
"In a cover article published today (23 February 2006) in Science, the team of researchers from Carnegie Museum of Natural History, Nanjing University, and Chinese Academy of Geological Sciences describe a fossilized skeleton of Castorocauda lutrasimilis ([Castoro] - Latin for beaver, [cauda] - Latin for tail, [lutra] -Latin river otter] and [similis] - Latin for similarity). Castorocauda had a beaver-like tail, strong arms for digging, and sharp teeth specialized for aquatic feeding, similar to the modern river otter." Castorocauda is preserved with a pelt (guard hairs and under furs), making it the most primitive-known mammal to be preserved with hairs. Carbonized in the fossil, the short and dense under-furs were to keep water from the skin; the longer guard hairs are preserved as impressions on the fossil slab. Fossilized furs of this animal provide fresh evidence on phylogenetic evolution of mammalian fur – this kind of specialized pelt developed well before the rise of modern mammals. All previously discovered fossils with fur belong to the more derived taxa within the Mammalia or mammalian crown group.

"Its lifestyle was probably very similar to the modern day platypus," said Dr. Zhe-Xi Luo, curator of Vertebrate Paleontology at Carnegie Museum of Natural History. "It probably lived along river or lake banks. It doggy-paddled around, ate aquatic animals and insects, and burrowed tunnels for its nest."

Dr. Luo pointed out that, perfectly shaped for aquatic life, Castorocauda had a broad and scaly tail that propelled it through water just like the modern beaver. Its tail vertebrae are also similar to those of beavers and otters. Because Castorocauda is not related to modern placentals, its adaptation for swimming is a convergent evolution to the modern beaver and modern river otter, both of which are placentals.

"Uncovered from the Middle Jurassic Jiulongshan Formation of the Inner Mongolia Region, dated approximately 164 million years ago, Castorocauda is the earliest-known mammal that had specialized skeletal and soft-tissue features for swimming and teeth for eating fish. This significant fossil offers the first evidence that some Mesozoic mammals occupied the semi-aquatic niche and that Mesozoic mammals as a whole had a much great ecological diversification than previously thought."

(Text and illustration courtesy Carnegie Museum News)


Answers.com article about Castorocauda
Wikipedia entry for Castorocauda

 





  Repenomamus turns tables on dinosaurs
  January, 2006

Most Mesozoic mammals were tiny, probably nocturnal and insectivorous. They are popularly seen, when thought about at all, as scampering to keep out of the way of the predatory dinosaurs. One specimen of a small feathered dinosaur, Sinosauropteryx prima, was found which contained remains of three individuals of small mammals, two Zhangheotherium and one of the multituberculate Sinobaatar. Not all Mesozoic mammals were so small, however. Repenomamus, a triconodont known from the famous fossil beds at Liaoning China that have produced so many beautiful early birds, is known from several dozen complete specimens. There are two species, Repenomamus robustus, about the size of the American opossum, and Repenomamus giganticus, about 50% larger. In Januray 2006, a complete skeleton of R. robustus was prepared and described which contained, in the area occupied by the stomach, the partial remains of a small herbivourous dinosaur, Psittacosaurus. The fact that some of the long bones were found in articulation suggests that "the juvenile Psittacosaurus was dismembered and swallowed as chunks."
     

Left: Artists reconstruction of Repenomamus chasing a juvenile Psittacosaurus. Center: The skeleton of Repenomamus containing the dinosaur remains. Right: Skeleton of Repenomamus giganticus, the largest known Mesozoic mammal.

Hu, Yaoming, Jin Meng, Yuanqing Wang and Chuankui Li, 2006: "Large Mesozoic mammals fed on young dinosaurs" Nature Vol. 433(13):149-152


 Cretaceous fossil, Maastrichtidelphys meurismeti
 suggests transatlantic connection of North American and
 Europe earlier than previously thought - June, 2005

 

"A new mammal more than 66 million years old whose origins are in South Dakota has been identified in the Netherlands. Dr. James Martin (Geol71), professor emeritus, geology and geological engineering, identified the mammals while conducting research for the School of Mines Museum of Geology. Two amateur collectors from the Netherlands, Roland Meuris and Frans Smet, discovered the fossil, which consists of a tooth. When paleontologists at the Natural History Museum of Maastricht showed a photograph to Martin, he was able to identify it because of his experience with fossils at the School of Mines Museum of Geology. The Museum of Geology is an epicenter for the study of fossils, both regionally and worldwide. Although the museum has a collection of fossils from around the world, specimens from South Dakota make up a majority of the collections. Based upon these specimens, Dr. Martin was able to recognize the mammal. In addition to the museum’s library of fossils, Dr. Martin was able to draw on his personal experience with them. Some of the fossils that he collected in his senior year of college at the School of Mines helped him in identifying the new specimen. The new species has been named after its discoverers and is called Maastrichtidelphys meurismeti, which means the “Maastricht opossum of Meuris and Smet.” The fossil’s closest relative is found in western South Dakota in Meade County. This relative suggests that these mammals were able to travel across a before unknown trans-Atlantic route. “This find has world-wide implications,” Dr. Martin said. “It changes the way we look at the history of climates and animal distribution.” According to Martin, paleontologists had assumed that these mammals had not made the crossing from North America until the Eocene epoch, which was 10 million years after the extinction of dinosaurs. The new fossil find suggests that during the end of the Cretaceous period, which was the end of the Age of Dinosaurs, temporary trans-Atlantic land bridges existed. The new find is so important because it changes views on the timeline of the distribution of animals through history."

The description of Maastrichtidelphys appears in the Journal of Mammalian Evolution. The complete reference is:
Martin, J.E., Case, J.A., Jagt, J.W.M., Schulp, A.S. & Mulder, E.W.A. (2005). “A New European Marsupial Indicates a Late Cretaceous High-latitude Transatlantic Dispersal Route.” Journal of Mammalian Evolution vol. 12, Nos. 3/4, 495-511.
Source of news article.

  Phoberomys pattersoni, huge South American rodent
  announced September, 2003

World's Largest Rodent: Buffalo-Size Fossil Discovered

By John Roach

for National Geographic News   September 22, 2003 The fossil remains of a giant rodent that weighed an estimated 1,500 pounds (700 kilograms) is helping scientists form a clearer image of what northern South America was like some eight million years ago.

Heralded as the world's largest rodent, Phoberomys pattersoni looked more like a giant guinea pig (Cavia porcellus) than an oversized house rat (Rattus rattus) and it apparently flourished on a diet of vegetation, not scraps dropped on the kitchen floor.

"Phoberomys was most likely a herbivore, and I seriously doubt it was a pest," said Marcelo Sánchez-Villagra, a paleontologist at the University of Tübingen in Germany. "When thinking of Phoberomys, think guinea pig, not rat."

Orangel Aguilera, a zoologist with the Universidad Francisco de Miranda in Venezuela, together with a colleague, Ascanio Rincon, discovered the Phoberomys fossils in 1999 in the Urumaco Formation, a desert region near the northwest coast of Venezuela.

Sánchez-Villagra and Ines Horovitz, a professor of organismic biology, ecology, and evolution at the University of California, Los Angeles, together with Aguilera, performed detailed studies of the fossils beginning in 2002. The team's report was published in the September 19, 2003 issue of the journal Science.

"It's really an exciting find," said Louise Emmons, a field biologist who specializes in neotropical mammals at the Smithsonian Institution in Washington, D.C.

 
Original article in Science  (abstract only)

  Australian cave fossils include a complete skeleton of the
  marsupial lion  Thylacoleo carnifax,
  July, 2002


Thylacoleo carnifex skeleton and reconstruction Interior of Nullabor cave

Illustrations courtesy Western Austrailan Museum

An astonishing collection of fossil animals from southern Australia is reported by scientists. The creatures were found in limestone caves under Nullarbor Plain and date from about 400,000-800,000 years ago. The palaeontological "treasure trove" includes 23 kangaroo species, eight of which are entirely new to science. Researchers tell Nature magazine that the caves also yielded a complete specimen of Thylacoleo carnifex, an extinct marsupial lion.
In total, 69 vertebrate species have been identified in three chambers the scientists now call the Thylacoleo Caves. These include mammals, birds and reptiles. The kangaroos range from rat-sized animals to 3m (nearly 10ft) giants. Story from BBC News


  Eomaia scansoria, earliest eutherian mammal
  discovered in China - April, 2002

Earliest Known Ancestor of Placental Mammals Discovered

By John Roach
for National Geographic News April 24, 2002

Researchers today announced the discovery of the earliest known ancestor of the group of mammals that give birth to live young. The finding is based on a well-preserved fossil of a tiny, hairy 125-million-year-old shrewlike species that scurried about in bushes and the low branches of trees.
"We found the earliest ancestor, perhaps a great uncle or aunt, or perhaps a great grandparent—albeit 125 million years removed—to all placental mammals," said Zhe-Xi Luo, a paleontologist at the Carnegie Museum of Natural History in Pittsburgh, Pennsylvania. "It is significant because a vast majority of mammals alive today are placentals." Cows, rats, monkeys, lions, tigers, and pandas are placentals. Dogs, rhinoceroses, tree sloths, horses, and whales are placentals. And, of course, humans are placentals.

The fossil of the animal, named Eomaia scansoria, was found in the fossil-rich region of Liaoning Province in China, which has also produced ancient evidence of feathered dinosaurs and primitive birds. Eomaia, which means "ancient mother" in Greek, was five inches (14 centimeters) long and weighed no more than 0.9 ounces (25 grams). the discovery in the April 25 issue of Nature. The finding indicates that the earliest extinct relatives of placentals had a much greater diversity than previously thought, Luo said, and "tells us about the ancestral morphology from which all placentals would have descended."


Full article can be found online at National Geographic News

Abstract from the article in Nature:

"The skeleton of a eutherian (placental) mammal has been discovered from the Lower Cretaceous Yixian Formation of northeastern China. We estimate its age to be about 125 million years (Myr), extending the date of the oldest eutherian records by about 40– 50 Myr. Our analyses place the new fossil at the root of the eutherian tree and among the four other known Early Cretaceous eutherians, and suggest an earlier and greater diversification of stem eutherians than previously known (the latest molecular estimate of the diversification of extant placental orders is 104–64 Myr). The new eutherian has limb and foot features that are known only from scansorial (climbing) and arboreal (tree-living) extant mammals, in contrast to the terrestrial or cursorial (running) features of other Cretaceous eutherians. This suggests that the earliest eutherian lineages developed different locomotory adaptations, facilitating their spread to diverse niches in the Cretaceous."
Full article is in Nature: pdf format

Note: Wible, Rougier and Novacek (2005) commented on Eomaia as follows: "The oldest known eutherian skull is that of Eomaia (Ji et al., 2002) but it is badly damaged and preserved mostly as molds and impressions providing few details."

  Hadrocodium wui, smallest known Mesozoic mammal,
  discovered in 2001

Researchers discover fossil of tiny mammal from Early Jurassic
Discovery provides important new evidence on the earliest evolution of mammals
 Pittsburgh... An international team of researchers led by Carnegie Museum of Natural History Vertebrate Paleontologist Dr. Zhe-Xi Luo has discovered a 195-million-year-old fossil mammal. The new mammal is the smallest known for the Mesozoic Era and represents a new branch on the mammalian family tree.

In an article published today in the prestigious journal Science, the team of American and Chinese scientists described this new mammal as having a precociously large brain and the middle ear of modern mammals. It suggests that these two features may have evolved together.

Previously, these important mammalian traits could only be traced to the late Jurassic (approximately 150 million years ago). This discovery pushes back their origins by some 45 million years to the Early Jurassic.

The new species is named Hadrocodium wui for its exceptionally large brain ([hadro] – Greek for "large and full" and [codium] – Greek for head). The fossil has widespread implications to scientists piecing together the earliest mammalian evolutionary history.

"Mammals differ from non-mammalian vertebrates by possessing a very large brain and an advanced ear structure," said Dr. Luo. "It has been a challenge for scientists to trace the origins of these important mammalian features in the fossil record."

The newest addition to the mammalian family tree also happens to be the tiniest mammal known from the Mesozoic Era and one of the smallest mammals ever. Based on the size of its well-preserved skull, it is estimated that the whole animal weighed only two grams, less than the weight of a paper clip. With such a tiny body, its diet was likely limited to very small insects and small worms. Its enlarged brain and very small body also tell scientists that the animal had a very high metabolism, forcing it to continuously eat.

Co-existing with the extremely small Hadrocodium in the Early Jurassic were several other primitive mammals with much larger body size. "This tiny creature greatly stretches the range of body size for the earliest known mammals," added Dr. Luo.

Hadrocodium is a distant and extinct relative of living mammals such as the platypus, kangaroos and primates. It is more closely related to mammals that exist today than the primitive cynodonts or "mammal-like reptiles."

Hadrocodium was discovered in the famous Lufeng Basin in Yunnan Province, southwestern China. It is one of the most prolific sites for early Jurassic land vertebrates. The Mesozoic Redbeds of the Lufeng Basin have yielded many vertebrate fossils. Among the fossils that have been unearthed are the carnivorous dinosaur Dilosphosaurus, the prosauropod Lufengosaurus, crocodiles, and lizard-like animals, herbivorous mammal-like reptiles, and some of the earliest mammals ever discovered.

Dr. Luo's research team includes Alfred W. Crompton of Harvard University and Ai-Lin Sun of the Chinese Academy of Sciences.

Funding for this research was provided by the National Science Foundation, National Geographic Society, Carnegie Museum of Natural History's Putnam Funds and Museum of Comparative Zoology at Harvard University.

(Text and illustrations courtesy Carnegie Museum News)


Left: Reconstruction of Hadroconium wui. Right: Dr. Zhe-Xi Luo is holding up the tiny skull of Hadrocodium for a close look.


 Sea-going sloths from Peru
 announced May, 1995

   

(Above) The skull of Thalassocnus yaucensis, the youngest species of the aquatic sloth. (Journal of Vertebrate Paleontology)

   
Image used by permission of the artist, Bill Parsons

"GROUND sloths (Gravigrada, Xenarthra) are known from middle or late Oligocene to late Pleistocene in South America and from late Miocene to late Pleistocene in North America. They are medium to gigantic in size and have terrestrial habits. Discovery of abundant and well preserved remains of a new sloth (Thalassocnus natans), in marine Pliocene deposits from Peru drastically expands our knowledge of the range of adaptation of the order. The abundance of individuals, the absence of other land mammals in the rich marine vertebrate fauna of the site, and the fact that the Peruvian coast was a desert during the Pliocene suggest that it was living on the shore and entered the water probably to feed upon sea-grasses or seaweeds. The morphology of premaxillae, femur, caudal vertebrae (similar to those of otters and beavers) and limb proportions are in agreement with this interpretation." [Nature 375, 224 - 227 (18 May 1995)] The research was reported by C. de Muizon and H. Greg McDonald in Nature.

In 2004, de Muizon, McDonald, Salas and Urbina reported on the evolution of the feeding strategy of the sloths:
"The aquatic sloth Thalassocnus is represented by five species that lived along the coast of Peru from the late Miocene through the late Pliocene. A detailed comparison of the cranial and mandibular anatomy of these species indicates different feeding adaptations. The three older species of Thalassocnus (T. antiquus, T. natans, and T. littoralis) were probably partial grazers (intermediate or mixed feeders) and the transverse component of mandibular movement was very minor, if any. They were probably feeding partially on stranded sea weeds or sea grasses, or in very shallow waters (less than 1 m) as indicated by the abundant dental striae of their molariform teeth created by ingestion of sand. The two younger species (T. carolomartini and T. yaucensis) were more specialized grazers than the three older species and had a distinct transverse component in their mandibular movement. Their teeth almost totally lack dental striae. These two species were probably feeding exclusively in the water at a greater depth than the older species." [Journal of Vertebrate Paleontology: Vol. 24, No. 2, pp. 398–410.

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