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Temporal range: Paleocene-Holocene, 63–0 Ma
Common squirrel monkey (Saimiri sciureus)
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Primates
Suborder: Haplorhini
Pocock, 1918[1]

Haplorrhini (the haplorhines or the "dry-nosed" primates, the Greek name means "simple-nosed") is a clade containing the tarsiers and the simians (or anthropoids). The name is also spelt Haplorrhini.[2] The simians include catarrhines (Old World monkeys and apes including humans), and the platyrrhines (New World monkeys).

The extinct omomyids, which are considered to be the most basal haplorhines, are believed to be more closely related to the tarsiers than to other haplorhines.

Haplorhines share a number of derived features that distinguish them from the strepsirrhine "wet-nosed" primates (whose Greek name means "curved nose"), the other suborder of primates from which they diverged some 63 million years ago. The haplorhines, including tarsiers, have all lost the function of the terminal enzyme that manufactures vitamin C, while the strepsirrhines, like most other orders of mammals, have retained this enzyme and the ability to manufacture vitamin C.[3] The haplorhine upper lip, which has replaced the ancestral rhinarium found in strepsirrhines, is not directly connected to their nose or gum, allowing a large range of facial expressions. Their brain to body ratio is significantly greater than the strepsirrhines, and their primary sense is vision. Haplorhines have a postorbital plate, unlike the postorbital bar found in strepsirrhines. Most species are diurnal (the exceptions being the tarsiers and the night monkeys).

All anthropoids have a single-chambered uterus; tarsiers have a bicornate uterus like the strepsirrhines. Most species typically have single births, although twins and triplets are common for marmosets and tamarins. Despite similar gestation periods, haplorhine newborns are relatively much larger than strepsirrhine newborns, but have a longer dependence period on their mother. This difference in size and dependence is credited to the increased complexity of their behavior and natural history.

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  • Lab Lecture 6
  • How to Pronounce Haplorhini
  • Lecture 13 Primates


So for this lab activity we're going to be talking about Primate Taxonomy. And the emphasis here isn't just going to be on describing the major primate groups, but also on ways to classify them based on their physical characteristics. So the objectives for this lab include comparing and contrasting primates versus nonprimates, and then identifying each major classification of primates based on skeletal characteristics. We'll also be talking about some soft tissue characteristics and I know Dr. Gursky covers this in depth in her lectures. But the emphasis on the lab will be on skeletal remains and the cusps that we have and the skeletons of various primates. So to get us started, what is unique about the order of primates, in terms of skeletal characteristics? Primates have a, an increased reliance on vision. And as a result, we see increased bony protection around the eyes. This manifests in a postorbital bar or postorbital closure behind the eyes to help protect and enclose that Orbits. Primates have relatively larger brains than non-primates. We also have a heterodont dentition and that means that we have more than just one tooth type in our dental arcade. So if you think of a creature like a great white shark, all of their teeth are the same exact shape. They're that singular, unicuspid shape. Whereas primates have incisors, canines, premolars, molars and that kind of thing. We have many different tooth types. And that's reflective of our more generalized diet. We can eat a lot of different things. We also have anteriorly facing orbits, so our orbits are oriented more front than laterally. We are pentadactyls, we have five digits on our hands and feet, and we have a generalized limb structure as well. In terms of soft tissue characteristics, primates have nails instead of claws. So we have fingernails instead of claws like a cat. A decreased reliance on olfaction. Meaning, we don't rely as much on our sense of smell. And you can see this not only in the soft tissue, but also in the skeleton. Primates have a reduced snout length compared to non-primates. There are also some social characteristics that are indicative of primates. We have increased infant dependency, very complex social behavior, and enhanced vision. So here we have two images. One of a primate and one of a non-primate. And looking at the soft tissue we notice a few things. The one on the left, which is a primate, has more anteriorly oriented orbits, so the eyes are facing more forward. The snout is much shorter than the image on the right. The brain on the primate is a little bit larger. And just going through that list of characteristics one by one and looking at the suite of traits we can diagnose okay, one of these is a primate, the other is not. You can also do the same thing using the skeleton. So here we have a Rhesus monkey and then a Grey Squirrel. So what are some of the skeletal characteristic I described? First of all, we look at brain size. We notice that the Rhesus Monkey has a much larger brain relative to the face, than does the Grey Squirrel. We can also talk about post orbital bar or closure and where you are looking for that is right here on the Rhesus Monkey. Notice how that is enclosed, whereas on the grey squirrel, here I'm circling in red there is no post orbital bar or closure. So, we know that the grey squirrel cannot be a primate. Other traits to look for include snout length, so the grey squirrel has this very long snout, which suggests that it is much more reliant on the sense of smell, than is this rhesus monkey. And just going through those traits again, like with the soft tissue, one by one we can say, okay, the Rhesus Monkey is in fact a primate, whereas the Grey Squirrel is not. And you can do this diagnosis even when you're not told the species name. You can generate these classifications yourself using those traits. Now within the Order primates, there're two suborders in the modified taxonomy. And they are Strepsirhini and Haplorhini. Strepsirhini includes things like your lemurs, lorises and gallegos, while Haplorhini includes monkeys, apes, humans and Tarsiers. And the reason there are many different taxonomic schemes for primates, is mainly because of Tarsiers. Tarsiers are just a little strange. They have a suite of traits that makes them very difficult to classify. So we'll talk about what makes tarsiers unique in a second. But first, let's see what will distinguish Strepsirhines from Haplorhines. So Strepsirhini, those lemurs, lorises and gallegos, have post orbital bars. They do not have the full closure posterior to the orbits. They also have a unique trait called a Dental Comb. And a dental comb will be found on the mandible, on the mandibular interior dentation. And it basically looks like the incisors and canines are sticking out at a 90 degree angle, from the rest of the teeth. And that's related to some behaviors that we see in Lemurs, Lorises, and Gallegos. Strepsirhines are also characterized by an unfused mandible and frontal. So that means when you're looking at the skeletal remains, you can actually see the sutures in the frontal along the mid-line, and also in the mandible as well, along mid-line. They're in two parts rather than infused into one full bone. Strepsirhinis have smaller brains relative to Haplorhines, and they also have a unique trait called a Grooming Claw, which you'll see in a second. And that will be found on their hands. They also all have tails, a split upper lip which you can see on the soft tissue, and many are nocturnal. And we can see that in some cases in their vision complexes. For Haplorhines, they have the full postorbital closure. Sometimes you'll hear it referred to as a postorbital plate, and that means the orbit is fully enclosed, posteriorly. They do not have a dental comb. All monkeys have tails. But hominoids, which are your apes, do not have tails. Haplorhines have have fused mandibles and frontals, except the tarsier, they have larger brains generally than Strepsirhines except the tarsier, no grooming claw and they're Diurnal. Again, except the tarsiers. You can see here where the tarsiers is being a little distinctive from other haplorhines. But primatologists agree that it is most closely related to Haplorhines rather than Strepsirhines, hence why it's classified with them. So looking at some of these traits. Here is a picture of a grooming claw. So on this right hand drawing of a lemur, you can see it right there. It's that little crooked toe, and you can see it right here as well. Those would be grooming claws. In terms of soft tissue, we can look at things like the split upper lip. You'll notice that on the monkey on the right, the lip is one full lip, whereas with a lemur it's a split upper lip. It's hard to see because the ring-tailed lemur has that black snout, but it's a split upper lip like you might see in a cat, for example. Strepsirhines have a relatively larger reliance on olfaction than Haplorhines and you can see than in the length of the snout, verses on the monkey. Brain size as well is something you can consider, and in the soft tissue if you could see the hands, you would look for that grooming claw as well. In addition to looking at the soft tissue, we can also consider the bony skeleton. So starting with the dental we see on the Strepsirhine picture on the left, that there are these anterior dentition that are out at a 90 degree angle relative to the other teeth, which is absent in our Haplorhines over here. We just have normal incisors like we would see in our own mouths for example. In addition, you can consider things like the postorbital bar versus closure. On the Strepsirhine here, notice that there's just this bony bar, that I've outlined in red. Whereas on the Haplorhine, we have a full bony plate behind the orbit. Other traits would be things like, look at the relative length of the snout in some cases on the lemur on the left, it's much longer than on the haplorhine. And also the level of encephalization, the brain size. The haplorhines on average will have bigger brains. And of course, our tarsiers are going to be the exception for a lot of these considerations. Within Strepsirhini, there are two, and for orders Lemuriformes and Lorisiformes, we're not going to ask you to be able to distinguish them in lab, but you should be aware that there are these two Infraorders that exist and Dr. talks about them extensively in the formal lectures as well. Within Haplorhini there're three Infraorders: Our Tarsiiformes, Platyrrhines and Catarrhines. Tarsiiformes include Tarsiirous, not surprisingly, Platyrrhini are your new world monkeys and Catarrhini are old world monkeys and apes. So let's look at how to distinguish each of these groups. Tarsiers are odd balls in the primate family, have an unfused mandible and frontal. So on the skull, you would expect to see a suture here and here as well. It's a little hard to see in the picture, but I just drew it on where the rough positions would be on the picture. There's full post orbital closure. Tarsiers do have a tail if you have the post cranial skeleton. They're nocturnal, and they have an incredible reliance on vision. And you can see this manifested in the size of the orbits. Just look at the size of these orbits, relative to the overall shape and size of the cranium. One eyeball is essentially as large as the brain for a tarsier so, huge orbits here. They also have a grooming claw on the second and third toes as well. So that will be a diagnostic from other haplorrhines. In terms of comparing Platyrrhini versus Catarrhini, a few traits that distinguish the two groups include the dental formula, and many of the structures around the ear and finally tails versus no tails. So for the dental formula, platyrrhines are 2:1:3:3. They have three premolars. They can be 2:1:3:2 for callitrichids. And callitrichids are things like tamarinds and marmosets. They're in that group of New World Primates. So they only have two molars, but all Platyyrhini has three premolars, and that will distinguish all of them from Catarrhini, which have the 2:1:2:3 dental formula. So two incisors, one canine, two pre-molars, three molars. Platyrrhines have a bony ring around the temporal area, while Catarrhines have a bony tube. Platyrrhines also have a much larger external auditory meatus than Catarrhines. And this is relative to other surrounding structures than the overall size of the skull. Platyrrhines have tails, some of which are prehensile, and prehensile means that they can basically be used as a fifth limb. So if you've ever seen a picture of a monkey hanging by its tail, that's a monkey that has a prehensile tail that can actually do that. Catarrhines eat, within Catarrhini, there're tails in old world monkeys only. Apes including humans do not have tails. And finally for soft tissue consideration, Platyrrhines have a flat nose, while Catarrhines have a more hook like nose. So, looking at some of the soft tissue traits, we can see the nasal shape differs between these monkeys, so we have howler monkeys or Platyrrhines on the left and baboons or Catarrhines on the right. And because we have monkeys here, in both cases there're tails. So moving on to the hard tissue, the bony skeleton, let's talk about that dental formula. So Platyrrhines have remember three pre molars and that distinguishes them 100% of the time from Catarrhines. So counting the teeth here we have two incisors, one canine, three premolars and three molars. That means the individual on the left is a Platyrrhine, a new world monkey. And that's different from the three molars to premolar structure that we see in the Catarrhines. For other bony features that will distinguish these two groups, one that is important, includes the External Auditory Meatus. And that is located right here. And compare that to the overall size of the skull, and the surrounding features. It's quite large, overall. For the Catarrhine on the right, the external auditory meatus is right here. It's actually very small relative to the overall size of this skeleton. We can also look at the dental formula as well. So we have three molars on this Catarrhine, two pre-molars, versus three pre-molars, two molars over here. The other main bony feature I talked about was in the temporal area and that is the difference in the bony tube in Catarrhines and the bony ring in Platyrrhines. So where you look for that is on the interior aspect of the skull. And the easiest way to do it, is find the external auditory meatus, and track its projection towards midline. So on our Platyrrhine over here, the external auditory meatus is right there. So it's that whole that I'm circling in red. And the bony tube structure is located right here. It's a very bulbous area. Compare that to the Catarrhine on the right. So the external auditory meatus will be right here, which I'm highlighting in red and drawing an arrow to. And the bony tube structure is much longer, and you can see it on both the right and the left sides. It's this right here. That will be only found in Catarrhines and not Platyrrhines. Now within Catarrhini there are two groups that we'll also ask you to distinguish based on physical remains. And those are the Superfamilies of Cercopithecoidea and Hominoidea. So Cercopithecoidea are our Old World monkeys. Hominoids are apes. And humans are included as hominoids, because we are apes. The two groups mainly are different in terms of molar cusp pattern and the other items we see here. Cercopithecoids have bilophodont molars, whereas Hominoids have Y-5 molar cusp pattern. Cercopithecoids also tend to have a longer snout than Hominoids. Still a little bit more increased reliance on olfaction than Hominoids. Cercopithecoids also have a narrow thorax and they have tails. They're monkeys so they have tails. Whereas apes have a broader thorax and no tails. And you can assess that if you have the post cranial remains. For the dental remains, let's talk about the Dental Pattern. So on the right, we have Hominoid and looking at the three molars, they all have the Y-5 pattern. And what that means is there're five cusps on each of these molars. So I'm circling the cusps in red on the first molar here. And within these five cusps, you can draw a Y in the crevices between them. And the Y opens laterally. And doing that on the M too as well, five cusps. They all have names but that doesn't matter for our purposes here it's just this shape. Five cusps and the Y in between. And compare that pattern to the Cercopithecoid dentition on your left. With Bilophidont molars, what that means is, we have two groups of cusps. Two bi, bi means two, and they are connected by horizontal ridges. So, here we have a cusp, a cusp, a cusp, a cusp, and if you look at it, the way I look at it, is you can almost draw across. So within Catarrhini, one of the things that you'll be doing in lab today is distinguishing between Cercopithecoids and Hominoids. And these are the two superfamilies of the Infraorder Catarrhini. Cercopithecoids are your Old World monkeys and Hominoids are apes. And apes includes everything from gorillas, chimpanzees, orangutans, to humans as well. Now when trying to decide between these two groups, one of the important features to look for are, is the Molar Cusp Pattern. Cercopithecoids have Bilophodont molars, and you'll see what those look like in a moment. Hominoids have Y-5 Molar Cusp Pattern. Elsewhere on the cranium you can look at snout length. Cercopithecoids have a slightly increased snout on average, compared to Hominoids, we have almost no snout at all. Cercopithecoids have a narrow thorax and a tail, while Hominoids have a broad thorax and no tail. So just remember that your apes don't have tails. People don't have tails. And we are apes and that is characteristic of all Hominoids. Looking at the dentition, Cercopithecoids have that bilophodont Molar Cusp Pattern. So on the left hand side here you see these are your molars and bilophodont means to and low for first in the fact that there're cusps can actually buy transverse bridges. So here's a cusp, here's a cusp, and there's a bridge in between connecting them. So cusp and cusp and then the ridge between them. And one of the things I look for when I assess bilophodont molars, is I look for four cusps, maybe more, that have those transverse ridges and are organized very symmetrically on the occlusal surface of the tooth. And that is different from our Hominoids. So looking at these teeth, for the hominoids, we have the y5 molar cusp pattern. So the five is referencing the number of cusps. So one, two, three, four, five and the Y refers to the shape of the ridges between them. So you see that pattern there. It's quite distinct from the bilophodont pattern. And that is going to be the easiest way for you guys to distinguish between Cercopithecoids and Hominoids in this lab. Within Hominoidea we can further break it down, the groups into families, subfamilies, and tribes. And Dr. Gursky goes into a lot of detail about all of these. For lab today the emphasis will be on distinguishing between up to the super family level of Cercopithecoidea versus Hominoidea. But it's important to remember that within Hominoidea we also have the families Hylobatidae and Hominidae. Within Hominidae, there're sub familys Ponginae, Gor, Orangutans, Gorillinae, which are Gorillas and then Homininae, which have two tribes, Panini your Chimps and Bonobos are closet really living relatives. And Hominini which are humans and are ancestors. Our Hominini ancestors. Now, when you're doing lab, one of the things you can use, is this flowchart, to help you classify the primates. So the first thing, when you're presented with an unknown skull, is to ask yourself, is this animal or primate? And I listed the traits that will help you make this consideration. If it's not a primate, that's where you stop for lab. We're not going to ask you to randomly identify any other animal. We're just interested in the primates. If it's a primate, is it a Strepsirhine or a Haplorhine? If it's a Strepsirhine, if it has, for example, a dental comb and only post-orbital bar, then you know it's a Strepsirhine and that's where you stop. If it's a Haplorhine, you need to distinguish if it's a Tarsier, a Platorrhine, or a Catarrhine. If it's one of those tarsiers, the little oddballs of the primate family, that's where you stop your classification. If it's a Platyrrhine, a new world monkey, if it has three premolars, and a large external auditory meatus, that's where you stop with your classification. And finally within Catarrhine, you just need to decide if it's a Cercopithecoid, if it has those bilophodont molars, or if it's a Hominoid. So, following this flow chart, let's do a couple demonstrations. So this is a skull. We're not sure what it's of. So the first question is, is it a primate? Well, looking at it, we notice it has a small brain relative to the overall size of the skull. It also has a very long snout, and we notice importantly that there is no post orbital bar or closure here, there's just a gap. So we know that this is not in fact a primate. It's actually a Coyote. Here is another example, so, first question: is it a primate? We have a fully enclosed orbit. We have a reasonably large brain. The snout isn't terribly long, so it's probably within the order of primates. For the next step of the flow chart, is it a Strepsirrhine or a Haplorhine? Well for Strepsirrhini we know we need to look for the dental comb. And notice that there is no dental comb for the anterior dentition. So we can immediately say that it's not a Strepsirhine, it must be a Haplorhine. Within haplirrhini, our three choices are Tarsier, Platyrrhine, or Catarrhine. Now a tarsier skull is quite small. It has the unfused mandible, in frontal, it has those orbits that are almost the same size as the brain. And that's not what we're seeing here. So we know it's not a Tersear. For Platyrrhini, what we wanna look for is dental formula and the structures in the temporal area, when you have a skull. So first, let's focus on the dentition. So we see this big canine here, and then counting back, we have three pre-molars and three molars. We also have a relatively large, easily visible, external auditory meatus. Based on this information, we know that this is a New World monkey, a Platyrrhine. So that's where our flowchart can stop. That's where our classification can stop for this lab. So, use these techniques, use this information as you do the lab, for primate taxonomy, and if you have any questions, any concerns, as always, feel free to contact your TA.



The taxonomic name Haplorhini derives from the Ancient Greek haploûs (ἁπλούς, "onefold, single, simple") and rhinos (ῥινός, "nose"). It refers to the lack of a rhinarium or "wet nose", which is found in many mammals, including strepsirrhine primates.[4]

Classification and evolution

Haplorhini and its sister clade, Strepsirrhini, diverged about 65 million years ago (mya). Approximately 5 million years later (60 mya), only a short time afterward from an evolutionary perspective, the infraorder Tarsiiformes, whose only remaining family is that of the tarsier (Tarsiidae), branched off from the other haplorhines[citation needed]. The fossil Archicebus may be similar to the most recent common ancestor at this time.

The other major clade within Haplorhini, the simians (or anthropoids), is divided into two parvorders: Platyrrhini (the New World monkeys) and Catarrhini (the Old World monkeys and apes). The New World monkeys split from catarrhines about 40 mya, while the apes (Hominoidea) diverged from Old World monkeys (Cercopithecoidea) about 25 mya. The available fossil evidence indicates that both the hominoid and cercopithecoid clades originated in Africa.[citation needed]

The following is the listing of the living haplorhine families, and their placement in the Order Primates:[1][5]


  1. ^ a b Groves, C.P. (2005). Wilson, D.E.; Reeder, D.M., eds. Mammal Species of the World: A Taxonomic and Geographic Reference (3rd ed.). Baltimore: Johns Hopkins University Press. pp. 127–184. OCLC 62265494. ISBN 0-801-88221-4. 
  2. ^ "Haplorrhini". Integrated Taxonomic Information System. Retrieved 2017-01-02. 
  3. ^ Pollock, J. I.; Mullin, R. J. (1987). "Vitamin C biosynthesis in prosimians: Evidence for the anthropoid affinity of Tarsius". American Journal of Physical Anthropology. 73 (1): 65–70. doi:10.1002/ajpa.1330730106. PMID 3113259. 
  4. ^ Ankel-Simons 2007, pp. 394–395.
  5. ^ Rylands AB, Mittermeier RA (2009). "The Diversity of the New World Primates (Platyrrhini)". In Garber PA, Estrada A, Bicca-Marques JC, Heymann EW, Strier KB. South American Primates: Comparative Perspectives in the Study of Behavior, Ecology, and Conservation. Springer. ISBN 978-0-387-78704-6. 

Literature cited

This page was last modified on 24 March 2017, at 04:52.
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