Evolution of the Platyrrhini Lecture 5

Question 1

In the Eocene and Oligocene there were no placental mammals in South America, only marsupials. When did placental mammals arrive?

Answer 1

In the Miocene (must have come from Africa). Lots of marsupials go extinct when primates and rodents arrive.

Question 2

How does the shape of the pterion differ in catarrhines and platyrrhines?

Answer 2

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

Question 3

How many premolars do platyrrhines have?

Answer 3

3 premolars

Question 4

How many premolars do catarrhines have?

Answer 4

2 premolars.

Question 5

Describe the ectotympanic of plats and cats?

Answer 5

Ring-like ectotympanic in Plats

Tubular ectotympanic in cats

Question 6

Where were the earliest platyrrhines found and when?

Answer 6

In Peru and Bolivia in the end of the Oligocene.

Question 7

Lots of fossils are found outside of where we find platyrrhines today. What does this suggest?

Answer 7

That the rainforest extended much further north and south.

Question 8

Describe Perupithecus.

Answer 8

1) Found in Peru
2) Early platyrrhine
3) Late Eocene? Poorly dated.
4) Found where rivers had been cutting into rocks.

Question 9

Describe Branisella.

Answer 9

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)

Question 10

Most South American monkeys don’t have ______ _______ but it looks like stem platyrrhines might have done.

Answer 10

Most S American monkeys don’t have sexual size dimorphism but it looks like these animals might have done.

Question 11

Why are some early platyrrhines considered to be terrestrial?

Answer 11

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

Question 12

Describe homunculus.

Answer 12

The person who found it claimed it was an early human ancestor but it’s actually a new world monkey.

Question 13

How many premolars did Homunculus have?

Answer 13

3 premolars (platyrrhine trait)

Question 14

Describe Dolichocebus gaimanensis

Answer 14

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

Question 15

Describe Soriacebus

Answer 15

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)

Question 16

Why do people think Soricebus is related to pithecines?

Answer 16

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.

Question 17

Describe Cebupithecia sarmientoi

Answer 17

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.

Question 18

Name an extinct species that is almost certainly related to howler monkeys and explain why.

Answer 18

Stirtonia tatacoenis

From middle Miocene in Colombia

The teeth have crests and howler monkeys are very folivorous.

Question 19

Describe the giant tamarin.

Answer 19

Lagonimico concludatus

Middle Miocene

Marmosets and tamarins were bigger in the past than they are now.

1 kg

Question 20

What is it called when animals get smaller over time?

Answer 20

Phyletic dwarfing.

Question 21

Why is Acrecebus considered to be the largest platyrrhine that ever lived.

Answer 21

It has the largest upper molar of any platyrrhine ever.

Late Miocene

Brazil

Question 22

Describe protopithecus.

Answer 22

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.

Question 23

There are very few derived traits that specific groups of platyrrhines have.

Name the derived traits of callitrichids, atelines and pithecines

Answer 23

callitrichids = loss of M3 and gives birth to twins

Atelines = prehensile tail

Pithecines = splayed canines

Question 24

Name the four time periods and places in which platyrrhines were found.

Answer 24

1) Late Oligocene:

Peru
Bolivia

2) Early Miocene

Argentina/Chile/Brazil/Caribbean

3) Middle/Late Miocene

Colombia/Brazil

4) Pleistocene/Recent

Brazil/Caribbean

Question 25

Describe Caipora.

Answer 25

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

Question 26

Describe Xenothrix.

Answer 26

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

Question 27

Taikai et al., 2000

Answer 27

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.