Clouds rolling over sharp peaks in the Swiss Alps.


Major Units of Geological Time
Definitive Events in Biological and Geophysical History

The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).

Other subdivisions reflect the evolution of life:
    the Archean and Proterozoic are both eons,
    the Palaeozoic, Mesozoic and Cenozoic are eras
        of the Phanerozoic eon.

The two million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.

(via Wikipedia)

Some people say that depicting geologic time and evolutionary history using a clock face design trivializes the truly incomprehensible time frame being depicted, and so is misleading.  

The time involved is in fact something very hard to get your mind around, but doesn't that make any depiction, even on a really long linear time line, misleading?  Probably.



Group: Neotheropoda

Classification: Cellular Life, Archaea, Proteoarchaeota, Eukaryota, Unikota, Opisthokonta, Holozoa, Filozoa, Metazoa, Eumetazoa, Planulozoa, Bilatera, Nephrozoa, Deuterostomia, Chordata, Craniata, Vertebrata, Gnathostomata, Eugnathostomata, Teleostomi, Euteleostomi, Sarcopterygii, Rhipidistia, Tetrapodomorpha, Eotetrapodiforms, Elpistostegalia, Stegocephalia, Tetrapoda, Reptiliomorpha, Anthracosauria, Batrachosauria, Cotylosauria, Amniota, Sauropsida, Eureptilia, Romeriida, Diapsida, Neodiapsida, Sauria, Archosauromorpha, Archelosauria, Archosauriformes, Crurotarsi, Archosauria, Avemetatarsalia, Ornithodira, Dinosauromorpha, Dinosauriformes, Dinosauria, Saurischia, Eusaurischia, Theropoda 

Definition: The group including the most recent common ancestor of Ceolophysis and modern birds, and all of that animal’s descendants 

Organisms Within: Zupaysaurus, Tachiraptor, Dilophosauridae (not examined here), Coelophysoidea (not examined here), Averostra (not examined here), & two miscellaneous genera without further placement. 

Time Range: Shown below, numbers on the left in millions of years. Though the only basal Neotheropods known are from the Triassic-Jurassic boundary, members of other groups are present much earlier than that, about 220 million years ago, implying that they must have evolved at around that time or older.  


Neotheropods differ from basal theropods mainly on a few skeletal points. The ilium bone in the pelvis, expanded towards the top of the animal (dorsally).  The snout is more narrow than in basal theropods, there are more vertebrae fused to the hips, there is a complete loss of the fifth digit of the foot (as shown below), and a general stiffening of the legs overall. 

By @ewilloughby

Like all early dinosaurs, Neotheropods were probably covered in a layer of primitive feathers - though some theropods groups would later lose feathers, the general line leading up to birds must have kept them, given that birds have feathers. They were bipedal, fast predators, and basal members of Neotheropoda were probably outcompeted by later animals, and even during their existence Coelophysoids were far more common. 

Source: @alphynix

Fossil Locations: It is fairly likely that Neotheropods also originated in Argentina, during that very rapid early diversification of dinosaurs in the region. This assessment is based mainly on the presence of basal theropods mainly in the region, though its possible that it also occurred in North America, where many Coelophysoids lived. Coelophysoids have also been found in Europe and Asia, and so given this widespread range of this group and its early evolution, as well as the locations of basal theropods, its reasonable to suppose that Argentina is where they started, unless evidence to the contrary comes to light.

Biogeography: Neotheropods spread throughout the globe, as described above; this was relatively easy due to Panagaea, however, most Coelophysoids congregated around North America and Europe. The two basal members of the group stayed in South America. Maps from Dr. Christopher Scotese. 

Read more about Zupaysaurus here!

Read more about Tachiraptor here! 

Posts on Coelophysoidea, Dilophosauridae, and Averostra to come soon!


Shout out goes to @chequitablr!

Miscellaneous Neotheropods not examined here that do not have further placement (links added as I do posts on them): 



A slice of the Triassic

Primitive conifers were one of the major groups of surviving trees in the harsh era that followed the near extinction of all life at the end of the Permian (see The 22cm example in the photo grew in a forest that was petrified by silica in what is now Gokwe in Zimbabwe, and comes from the family Woodwothia. At some point in its long journey to the present through geological time, chromium rich waters passed through the buried stone forest and deposited salts, resulting in the deep green tinge that picks out the inner structure of the wood beautifully.

Keep reading


A New “Golden Spike” Monument in Colorado Marks Geologic Time 
Andrew Alden [source] | October 31, 2013

For something that is supposed to keep track of 4 billion years of history, the geologic time scale is quite a fuzzy and slippery yardstick. After two centuries of careful research and argumentation, the world’s geologists have only recently adopted a system to literally nail down the different time periods taught in geology school.

Last week that project took another slow step forward as a “golden spike” was officially driven into a precise spot on the ground near Pueblo, Colorado, a benchmark for the beginning of the Turonian Age.

The Turonian is, in the ICS’ geologic timescale, the second age in the Late Cretaceous epoch, or a stage in the Upper Cretaceous series. It spans the time between 93.5 ± 0.8 Ma and 89.3 ± 1 Ma (million years ago).   [Wikipedia]

The Western Interior Seaway then divided North America into eastern and western halves; Appalachia and Laramidia.

24 million years after the Turonian ended, a massive asteroid struck the Yucatan, spelling the end for the dinosaurs.

Continue reading

[1] Photo courtesy Brad Sageman 
[2] Ichthyornis by S.V.Naugolnyh 
[3] Cover to American Journal of Botany, 89(12), 2002, showing leaf and pinecone litter on a Turonian Coastal Plain forest floor with the oldest unequivocal fossil monocot
[4] Zuniceratops by cheungchungtat
[5] The Turonian Stratotype Section near Pueblo, Colorado. Photos courtesy Bob Kay
[6] J of Sedimentary Research [X]  
[7] Chronostratigraphic chart


an·cient 1  


1. Of great age; very old.

2. Of or relating to times long past, especially those of the historical period before the fall of the Western Roman Empire (a.d. 476). See Synonyms at old.

3. Old-fashioned; antiquated.

4. Having the qualities associated with age, wisdom, or long use; venerable.


The notion of ancient has been rattling around the inside of my head for some long time now, and the longer I think about it, the more woolly an idea it becomes for lots of different reasons.


(One of the enigmatic stones of the Ring of Brodgar, erected about 5000 years ago but made of flagstone formed more than 300 million years ago, beneath the Moon, formed between 3 and 4 billion years ago.)

Whilst travelling around the country, and reading information about places, and talking to folk along the way, the places I am interested in often have this word tagged on to them. For instance, one Winter’s day on Chelmorton Low, the large hill overlooking the village of the same name, found me pondering the “ancient field system” of long, narrow strips of land there. The fact that I was viewing this green patchwork pattern from my seat atop one of the three still very present Bronze Age barrows or burial mounds made the term “ancient”, applied to the strip-cultivation seem altogether wrong. It is probably 600 or so years old and Saxon at the very earliest.

(ancient Viking carving, or graffiti, from about 1000 years ago, made on a lintel stone in a late Neolithic stalled cairn from about 4000 years before, Orkney)

When does something become “ancient”? We refer to clothes as ancient when they are worn out, people when they are either “too old” or nearing death, objects such as jewellery or furniture have to be older, maybe centuries old, whilst a tree may be considered ancient when it is maybe more than 500 years old . …. it is a very inexact term. And all the while I am acutely aware that there is a continuity, in matter, right down to its atoms. A new house can be built of quarried stone which was formed millions, billions of years ago. A new kitchen surface made of marble may contain fossils of truly ancient creatures. Even the carbon, oxygen and hydrogen atoms in horrible plastics have been in existence since before the stromatolites that we in turn, owe our own existence to, along the line somewhere….. Every new baby, every new life has contained within it the timelessly ancient coding of ancestry in its dna. It is enough to make my head feel like a pressure cooker. We are a constant recycling, though I’m not convinced it’s an upcycling of present matter. I watched a programme where biochemists were able to tag individual nitrogen atoms and trace their movement from one living organism, through decay and growth, into a completely different life form. Ancient-ness becomes meaningless. We are all made of the very particles which have existed since the very beginnings of time.  

This clock representation shows some of the major units of geological time and definitive events of Earth history. The Hadean eon represents the time before fossil record of life on Earth; its upper boundary is now regarded as 4.0 Ga (billion years ago).Other subdivisions reflect the evolution of life; the Archean and Proterozoic are both eons, the Palaeozoic, Mesozoic and Cenozoic are eras of the Phanerozoic eon. The two million year Quaternary period, the time of recognizable humans, is too small to be visible at this scale.