Evolution of the Platyrrhini Lecture 5 Flashcards
In the Eocene and Oligocene there were no placental mammals in South America, only marsupials. When did placental mammals arrive?
In the Miocene (must have come from Africa). Lots of marsupials go extinct when primates and rodents arrive.
How does the shape of the pterion differ in catarrhines and platyrrhines?
It is I shaped in platyrrhines and H shaped in catarrhines.
So a H shape indiactes either a catarrhine or a stem anthropoid.
In Plats the parietal touches the zygomatic and the frontal doesn’t touch the sphenoid.
In cats the zygomatic doesn’t touch parietal and the frontal does touch the sphenoid
How many premolars do platyrrhines have?
3 premolars
How many premolars do catarrhines have?
2 premolars.
Describe the ectotympanic of plats and cats?
Ring-like ectotympanic in Plats
Tubular ectotympanic in cats
Where were the earliest platyrrhines found and when?
In Peru and Bolivia in the end of the Oligocene.
Lots of fossils are found outside of where we find platyrrhines today. What does this suggest?
That the rainforest extended much further north and south.
Describe Perupithecus.
1) Found in Peru
2) Early platyrrhine
3) Late Eocene? Poorly dated.
4) Found where rivers had been cutting into rocks.
Describe Branisella.
1) Bolivia
2) Late Oligocene
Has anthropoid-like teeth and no derived platyrrhine feature.
So there was an anthropoid living in South America (we assume are related to platyrrhines)
Most South American monkeys don’t have ______ _______ but it looks like stem platyrrhines might have done.
Most S American monkeys don’t have sexual size dimorphism but it looks like these animals might have done.
Why are some early platyrrhines considered to be terrestrial?
They have very worn teeth and it is unusual to have worn teeth if you are arboreal. The closer to the ground you are, the more grit you eat which wears your teeth down.
No plats today are terrestrial so adaptations of plats today are very different to those in the past
Describe homunculus.
The person who found it claimed it was an early human ancestor but it’s actually a new world monkey.
How many premolars did Homunculus have?
3 premolars (platyrrhine trait)
Describe Dolichocebus gaimanensis
1) Early Miocene
2) Argentina
3) People thought it was related to squirrel monkeys due to the hole in the orbital finestra but this hole could be due to damage
Describe Soriacebus
1) Early Miocene
2) Procumbent lower incisors (not like a tooth comb, it is the sort of angling seen in pitehcines today)
3) 3-rooted premolars (also seen in parapithecids)
Why do people think Soricebus is related to pithecines?
Almost all primates have two rooted premolars, except stem anthropoids in Egypt. This is one of the things that has lead people to believe that these are related to pithecines.
Describe Cebupithecia sarmientoi
1) middle Miocene
2) Colombia
3) Dental and postcranial similarities to Pithecia
4) Upper and lower canines are splayed outwards, used for eating. The pithecines are the only primate that uses its canines for eating.
So this looks a lot like living pithecines.
Name an extinct species that is almost certainly related to howler monkeys and explain why.
Stirtonia tatacoenis
From middle Miocene in Colombia
The teeth have crests and howler monkeys are very folivorous.
Describe the giant tamarin.
Lagonimico concludatus
Middle Miocene
Marmosets and tamarins were bigger in the past than they are now.
1 kg
What is it called when animals get smaller over time?
Phyletic dwarfing.
Why is Acrecebus considered to be the largest platyrrhine that ever lived.
It has the largest upper molar of any platyrrhine ever.
Late Miocene
Brazil
Describe protopithecus.
The femur of protopithecus was one of the first primates to be named in the fossil record as a primate (earlier ones had been labelled as a cat or a cow)
They were really big (twice the size of extant plats)
Found in Brazil
Lived during Pleistocene
May have been a part of the Pleistocene megafauna extinctions.
There are very few derived traits that specific groups of platyrrhines have.
Name the derived traits of callitrichids, atelines and pithecines
callitrichids = loss of M3 and gives birth to twins
Atelines = prehensile tail
Pithecines = splayed canines
Name the four time periods and places in which platyrrhines were found.
1) Late Oligocene:
Peru
Bolivia
2) Early Miocene
Argentina/Chile/Brazil/Caribbean
3) Middle/Late Miocene
Colombia/Brazil
4) Pleistocene/Recent
Brazil/Caribbean
Describe Caipora.
1) From the Pleistocene
2) Brazil
3) Cave site in rainforest
4) Related to atelines
5) Cranium similar to Ateles
6) Suspensory postcranium
7) 20kg
Describe Xenothrix.
1) Holocene
2) Jamaica
3) 2 molars = callitrichid(?)
but teeth look nothing like the callitricid teeth and are much too big!
loss of M3 could be convergence
Taikai et al., 2000
the dentition of Branisella is very similar to that of Proteopithecus from the Late Eocene of Fayum, Egypt, except in the lower canine morphology, suggesting a close phyletic relationship between them.
