Petrolacosaurus, the oldest known diapsid reptile

Petrolacosaurus, an Upper Pennsylvanian reptile, presents a combination of features that place it within a distinct family of the Eosuchia while also evidencing strong relationships to the ancestral reptiles. It is therefore the earliest and most primitive representative of the largest assemblage of fossil and living reptiles, collectively called diapsids.     

Modern turtle origins: the oldest known cryptodire

The discovery of a turtle in the Early Jurassic(185 million years before present) Kayenta Formation of northeastern Arizona provides significant evidence about the origin of modern turtles. This new taxon possesses many of the primitive features expected in the hypothetical common ancestor of pleurodires and cryptodires, the two groups of modern turtles. It is identified as the oldest known cryptodire because of the presence of a distinctive cryptodiran jaw mechanism consisting of a trochlea over the otic chamber that redirects the line of action of the adductor muscle. Aquatic habits appear to have developed very early in turtle evolution. Kayentachelys extends the known record of cryptodires back at least 45 million years and documents a very early stage in the evolution of modern turtles.     

Discovery of the oldest known anthropoidean skull from the paleogene of Egypt

A group of primate fossils newly discovered in the Fayum badlands of Egypt is probably of Eocene age. The site is much older than the localities of previously known Egyptian early Tertiary primates. These finds include a crushed cranium that is the oldest skull found to date of a higher primate. This skull shows four characteristics of higher primates: a catarrhine dental formula, an ectotympanic at the rim of the auditory bulla, a fused frontal bone, and postorbital closure. Details of tooth structure (premolars and molars) and a possibly unfused mandibular symphysis resemble these parts in certain Eocene prosimians.     

The works of living social insects as pseudofossils and the age of the oldest known metazoa

Living organisms are known to create structures in ancient rocks that are indigenous but not primary and that have been mistaken for fossils. Examination of burrows recently reported as fossils from 10(9)-year-old sedimentary rocks indicates that they are not the same age as the rocks but were probably made by termites working down after water. The burrows are partially filled with material from a modern lateritic surface from which they descend into steeply dipping, decomposed silt-stones of the Zambian Copperbelt. In fact, no authentic record of Metazoa that are demonstrably coeval with rocks older than 680 million years is known.     

鸵鸟的全身骨骼特点

鸵岛的头骨薄而轻,颈椎１８个,胸椎８个,腰椎,荐椎和前几个尾椎愈合成腰荐骨,尾综骨退化,肋骨共８对,第１,７,８对为浮肋,肋骨均无钩突。胸骨扁平／／而平,无龙骨突。     

Skeleton of the Oldest Known Pinniped, Enaliarctos mealsi

A nearly complete skeleton of the archaic pinniped Enaliarctos, found in late Oligocene or early Miocene rocks (approximately 23 million years old) of California, provides new evidence on the origin of pinnipeds. Enaliarctos retains many primitive features expected in the hypothesized common ancestor of pinnipeds. Skeletal modifications seen in Enaliarctos document swimming adaptations and indicate that pinnipeds primitively used the axial skeleton and both fore and hindflippers as sources of propulsion. Elongate hindlimbs with prominent bony processes (reflecting powerful musculature) suggest that Enaliarctos was more active on land than modern pinnipeds.     

A vestige of Earth's oldest ophiolite

A sheeted-dike complex within the approximately 3.8-billion-year-old Isua supracrustal belt (ISB) in southwest Greenland provides the oldest evidence of oceanic crustal accretion by spreading. The geochemistry of the dikes and associated pillow lavas demonstrates an intraoceanic island arc and mid-ocean ridge-like setting, and their oxygen isotopes suggest a hydrothermal ocean-floor-type metamorphism. The pillows and dikes are associated with gabbroic and ultramafic rocks that together make up an ophiolitic association: the Paleoarchean Isua ophiolite complex. These sheeted dikes offer evidence for remnants of oceanic crust formed by sea-floor spreading of the earliest intact rocks on Earth.     

Radiolarians: Construction of Spherical Skeleton

The skeleton of spherical radiolarians, which consists basically of a network of hexagonally shaped structures, also contains some non-hexagonal structures, since a network made up entirely of hexagons cannot completely cover a spherically shaped organism.     

The oldest macroborers: lower cambrian of labrador

We have discovered numerous borings of Trypanites penetrating skeletons and synsedimentary cemented limestones in archaeocyathid reefs of the Forteau formation in southern Labrador. These are, to date, the oldest known macroborings. The discovery of these structures extends the record of large endolithic organisms 100 million years from the Lower Ordovician to the Lower Cambrian. This immediately postdates the appearance of metazoans with hard parts and confirms that endoliths have played a role in reef formation since the early Cambrian.     

Earliest known marsupials

The infraclass Metatheria has not been reported from deposits predating the mid-Cretaceous. Fossil material just recovered from Albian deposits in northcentral Texas has definite characteristics of the family Didelphidae and is submitted as being from the oldest known marsupials. The same locality has also produced remains referable to Eutheria, demonstrating a somewhat earlier divergence of these two important groups than was known before.