all right, so what is a tarantula?

krystal

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i always thought that tarantulas (or spiders belonging to the Theraphosidae family) were named as such because they were the biggest and hairiest species of all spiders.

so why are there "dwarf" tarantulas? isn't that a contradiction?

and what decides which spiders are tarantulas, anyway? do they have to pass a test? does "bob, the spider sorter" run around both tropical and desert areas with his magic tarantula wand singing, "i'm a tarantula, you're a tarantula, he's a tarantula, she's a tarantula", picking and choosing which spiders will hold the coveted "tarantula" title?

ack! someone please help me sort this whole thing out!
 

Arachnopuppy

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I've always thought that true spiders have eyes positioned in different places than tarantulas. But that's just me.
 

Steve Nunn

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Originally posted by krystal
i always thought that tarantulas (or spiders belonging to the Theraphosidae family) were named as such because they were the biggest and hairiest species of all spiders.

Hi Krystal,
All spiders from the family Theraphosidae are tarantulas(large or small), as you might term them. In Europe and many other countries, a tarantula is one actual species of wolf spider, Lycosa tarentula, from Europe. Europeans will just stick with "theraphosid" to describe this family (even though the Brittish Tarantula Society uses "tarantula" in it's name).

In the US however, tarantula is an acceptable term for all Theraphosidae. Many enthusiasts will also term other mygale families, such as the Dipluridae, a tarantula, although a more acceptable term for ALL mygale families would be "trapdoor spider", rather than "tarantula".

Using "common name" terminology such as this may land many an enthusiast in trouble with other enthusiasts, depending on where you live, which is why scientific names are always the way to go IMO.

Hope this helps,
Steve
 

Doug H

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this isnt very technical but tarantulas are the only "spider" to have backward pointing fangs other spiders have fangs that point toward each other.
 

Tranz

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I guess they share certain common physical traits and are joined by a common evolutionary branch. A miniature horse isn't any less a horse. The same goes with other species as well. However, there are always exceptions: Robert Reich and Mickey Rooney, for example.
 

Vys

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Mygalomorphs('old' spiders) have 2 pairs of booklungs and fangs that strike downwards, like pickaxes, whilst Araneomorphs('modern' spiders) have one pair of booklungs, and a second respiratory system much like that of insects, or something in that direction, and also their fangs go sideways instead, against each other, without any movement necessary of the head.
Anyway, there are these (2?) families of spids making up the third suborder,which I can't remember the name of right now,but anyhoo, these have 2 pairs of booklungs, like mygalomorphs, but fangs like araneomorphs.

At any rate, I have no clue what separates the Theraposidae from the other myga-families. Some biological details, no doubt. Like with Krystal, they're just the biggest and hairiest to me :D
 

Wade

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I believe the "toe pads" (I'm sure there's a better term) of therophosids are one of the features that distingish them from other mygalmorphs.

Wade
 

Steve Nunn

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Originally posted by Vys
Anyway, there are these (2?) families of spids making up the third suborder,which I can't remember the name of right now,but anyhoo, these have 2 pairs of booklungs, like mygalomorphs, but fangs like araneomorphs.

Hi Vys,
These are the Hypochilomorphae and they're what might be considered the 'living links' between the Mygalomorphae and the Araneomorphae. The morphological differences you stated are correct.

Cheers,
Steve
 

Venom

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A tarantula is a mygalomorph, of the family Theraphosidae, that is much hairier than any other mygalomorph order / family. If you've ever seen pictures of funnelwebs, pursewebs , trapdoors, etc. , then you have seen that they are ALL smooth, with only sparse hairs. They don't even have the super short hairs of the old world theraphosids, their exoskeletons are bare and smooth, except for a very few long sensory hairs.

Theraphosids ( "tarantulas" ) are the only mygalomorphs that have any large amount of hair ( whether short or long ) , and every theraphosid is covered in hair.
 

Steve Nunn

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Originally posted by monantony
Doug H
I think all mygalamorphs share the fang arrangement.. Maybe Steve can give us some of the taxonomic 'breaking points' that differentiate the mygales from each other....Man I wish I could have brought home some ctenids and diplurids from peru!
Tony
I'll give it to you roughly ;) This is fairly scientific, so all apologies if anyone ges confused, but this question isn't easily answered, sorry.


Since it's the Theraphosidae of relevance here I'll start with those. This may get a bit in depth here so bear with me :)

Within the mygalomorphs, the Theraphosidae, Glabropelma (from the family Paratropididae), the Barychelidae, one genus from the Nemesiiade and one genus from the Cyrtaucheniidae possess true claw tufts (in answer to Wades thoughts). Within the Theraphosidae and the Barychelidae, the presence of claw tufts is correlated with a number of characteristics. The females of all theraphosids and barychelids have few to no teeth on the paired claws, the third claw is bare and reduced, if not absent, the tarsal and metatarsal scopulae are very well developed, the carapace is relatively low with the eye tubercle elevated. Claw tufts are recognized as one synapomorphy (with parallelisms in the nemesiid and cyraucheniid) for the Theraphosidae, Glabropelma and Barychelidae, constituting the superfamily Theraphosoidea. This is just a rough overview of what constitutes this superfamily, there are other morphological traits too, although I won't be going into them now.

As you may or may not see, the Theraphosidae and the Barychelidae are very closely related to each other. Because the theraphosids are what we are most interested in, I thought I'd share a bit about their intrafamilial relationships with the barychelids (their closest family relative).

What defines a theraphosid from other mygale families: The well develpoed claw tufts and leg scopulae, in combination, are considered the autopomorphies, in association with the distinct maxillary lobes (shared also with the Paratropididae). Apart from the Ischnocolinae (theraphosid subfamily), the Theraphosidae have well-developed scopulae on all tarsi. That character is considered a synapomorphy for the theraphosids with a parallelism in the Barychelidae. Apart from that, no other character unique to the Theraphosidae is known. However, most theraphosids have particulary reduced spination of legs III and IV, which in the Barychelidae are as spinose as the Nemesiidae and the Dipluridae (two other families of the Mygalomorphae). Alhough the character does require further investigation before it can be asserted to be apomorphic.

MMkay, I'll try not to be so in depth with the other families as I just don't have time for one and most of you wouldn't be that into it anyway ;)

Paratropididae: Four autopomorphies are known. The scaly cuticle, the claw tufts are thin and weak if present at all, the unpaired claw is plesiomorphically absent on legs III and IV; and the cuticle of legs is clad only in strong setae and lacking fine hairs present in the other Theraphosoidina (the superfamily mentioned before). Paratropids are easily ID'd in the field due to a covering of mud on their cuticle.

Barychelidae: Three characters are known. The absence of a third claw, biserially dentate paired claws in males and well developed scopulae on tarsi I and II.

Nemesiidae: Three congruent characters support the monophyly of the Nemesiidae. The females and plesiomorphically the males , have biserially dentate paired claws, the paired claws are broad and the palpal claw has teeth on the promargin.

Dipluridae: Three characters indicate the diplurids are monophyletic. The posterior lateral spinnerets are very elongate (but with a secondary reduction in genera Microhexura and possibly also the subfamily Masteriinae), wide seperation of the posterior median spinnerets and the lowered caput plus the elevated thoracic region.

Hexathelidae: From what I understand there is only one autopomorphy within the hexathelids- numerous labial cuspules. Other characters need to be assesed which can also be found in other families, just not with the combination the hexathelids possess.

Mecicobothriidae: The monophyly of the mecicobothriids is indicated by he elongate cymbium that encloses the bulb, the pseudosegmented apical segment of the posterior lateral spinnerets and he longitudinal fovea, characters that, associaed with the elevated eye tubercle, low caput, and modified maxillary lobes, are unique in the Mygalomorphae.

Microstigmatidae: Four autopomorphies. The booklung apertures are round rather than oval, the thorax is elevated as high behind the fovea as the caput; the apical segments of the posterior lateral spinnerets are domed; and the cuticle is pustulose or scaly, not smooth as in most mygales. The combined presence of those features is unique in the Microsigmatidae, although all other features are found in other mygales.

Migidae: One autopomorphy; along the length of the outer surface of the cheliceral fangs are two low keels or ridges near the fang edge.

Actinopodidae: The actinopodids share a number of unique characters or combinations. Most evident are the maxillae which are square or at least subquadrate, a very elongate labium and short diagonal fang.

Ctenizidae: The Ctenizidae are characterized by the presence of stout curved spines on the lateral faces of the anterior pairs of legs of females.

Idiopidae: Three unique characters. The distal sclerite of the male palpal bulb is open along one side so that the second haematadocha extends down the the bulb almost to the embolus tip. Dimorphic lobes on the males cymbium is the second unique character. The third character is the unusual excavation on the prolateral palpal tibia of the males that is usually highlighted by a region of short thornlike spines.

Cyrtauchenidae: Three characters are possible autapomorphies, but all are ambiguous. Scopulae are present on tarsi I and II of all cyrtauchenid genera, except Kiama and Rhytidicolus. The second character is the presence of multilobular spermethecae. The third and weakest character is is that the spination of tarsi I and II is reduced in all cyrtauchenids, except Rhytidicolus.

Atypidae: The three aypid genera share four synapomorphies. The very elongate, curved maxillary lobes, the broad and obliquely truncated posterior median spinnerets, the rotated nature of the maxillae and the teeth on the paired and unpaired claws of males and females are raised on a common process giving the appearance of one multipectinate tooth.

Antrodiaetidae: Two characters are possible autapomorphies for the antrodiaetids. The third claw lacks teeth (but so does that of the Rastelloidina and Crassitarsae, in each of which it is considered a parallelism). Second, the form of the fovea is distinct from that of atypids, all Rastelloidina, and all Tuberculotae, except for possibly the mecicobothriids and the diplurids Microhexura and Carrai.

What I've mentioned here are the general differences between the families of the Mygalomorphae, these features alone probably aren't much use to anyone to key a spider down to ID it. There are many, many more features used in specific combinations, if you will, to key a mygale down. As you can see, it's a complicated task and usually, only experts are up to it. All of the information above is from Dr Raven's 1985 publication, The Spider Infraorder Mygalomorphae (Araneae): Cladistics and Systematics.

Cheers,
Steve
 
Last edited:

Steve Nunn

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Originally posted by Venom
Theraphosids ( "tarantulas" ) are the only mygalomorphs that have any large amount of hair ( whether short or long ) , and every theraphosid is covered in hair.
Hi,
Close, but not quite ;)

Many of the Barychelidae are also 'hairy' such as those from the genus Idiomnata, among others.

Cheers,
Steve
 

krystal

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wow--thanks everyone!

now, who wants to talk quantum physics? (just kidding)
 

Arachnopuppy

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Originally posted by Steve Nunn
I'll give it to you roughly ;) This is fairly scientific, so all apologies if anyone ges confused, but this question isn't easily answered, sorry.


Since it's the Theraphosidae of relevance here I'll start with those. This may get a bit in depth here so bear with me :)

Within the mygalomorphs, the Theraphosidae, Glabropelma (from the family Paratropididae), the Barychelidae, one genus from the Nemesiiade and one genus from the Cyrtaucheniidae possess true claw tufts (in answer to Wades thoughts). Within the Theraphosidae and the Barychelidae, the presence of claw tufts is correlated with a number of characteristics. The females of all theraphosids and barychelids have few to no teeth on the paired claws, the third claw is bare and reduced, if not absent, the tarsal and metatarsal scopulae are very well developed, the carapace is relatively low with the eye tubercle elevated. Claw tufts are recognized as one synapomorphy (with parallelisms in the nemesiid and cyraucheniid) for the Theraphosidae, Glabropelma and Barychelidae, constituting the superfamily Theraphosoidea. This is just a rough overview of what constitutes this superfamily, there are other morphological traits too, although I won't be going into them now.

As you may or may not see, the Theraphosidae and the Barychelidae are very closely related to each other. Because the theraphosids are what we are most interested in, I thought I'd share a bit about their intrafamilial relationships with the barychelids (their closest family relative).

What defines a theraphosid from other mygale families: The well develpoed claw tufts and leg scopulae, in combination, are considered the autopomorphies, in association with the distinct maxillary lobes (shared also with the Paratropididae). Apart from the Ischnocolinae (theraphosid subfamily), the Theraphosidae have well-developed scopulae on all tarsi. That character is considered a synapomorphy for the theraphosids with a parallelism in the Barychelidae. Apart from that, no other character unique to the Theraphosidae is known. However, most theraphosids have particulary reduced spination of legs III and IV, which in the Barychelidae are as spinose as the Nemesiidae and the Dipluridae (two other families of the Mygalomorphae). Alhough the character does require further investigation before it can be asserted to be apomorphic.

MMkay, I'll try not to be so in depth with the other families as I just don't have time for one and most of you wouldn't be that into it anyway ;)

Paratropididae: Four autopomorphies are known. The scaly cuticle, the claw tufts are thin and weak if present at all, the unpaired claw is plesiomorphically absent on legs III and IV; and the cuticle of legs is clad only in strong setae and lacking fine hairs present in the other Theraphosoidina (the superfamily mentioned before). Paratropids are easily ID'd in the field due to a covering of mud on their cuticle.

Barychelidae: Three characters are known. The absence of a third claw, biserially dentate paired claws in males and well developed scopulae on tarsi I and II.

Nemesiidae: Three congruent characters support the monophyly of the Nemesiidae. The females and plesiomorphically the males , have biserially dentate paired claws, the paired claws are broad and the palpal claw has teeth on the promargin.

Dipluridae: Three characters indicate the diplurids are monophyletic. The posterior lateral spinnerets are very elongate (but with a secondary reduction in genera Microhexura and possibly also the subfamily Masteriinae), wide seperation of the posterior median spinnerets and the lowered caput plus the elevated thoracic region.

Hexathelidae: From what I understand there is only one autopomorphy within the hexathelids- numerous labial cuspules. Other characters need to be assesed which can also be found in other families, just not with the combination the hexathelids possess.

Mecicobothriidae: The monophyly of the mecicobothriids is indicated by he elongate cymbium that encloses the bulb, the pseudosegmented apical segment of the posterior lateral spinnerets and he longitudinal fovea, characters that, associaed with the elevated eye tubercle, low caput, and modified maxillary lobes, are unique in the Mygalomorphae.

Microstigmatidae: Four autopomorphies. The booklung apertures are round rather than oval, the thorax is elevated as high behind the fovea as the caput; the apical segments of the posterior lateral spinnerets are domed; and the cuticle is pustulose or scaly, not smooth as in most mygales. The combined presence of those features is unique in the Microsigmatidae, although all other features are found in other mygales.

Migidae: One autopomorphy; along the length of the outer surface of the cheliceral fangs are two low keels or ridges near the fang edge.

Actinopodidae: The actinopodids share a number of unique characters or combinations. Most evident are the maxillae which are square or at least subquadrate, a very elongate labium and short diagonal fang.

Ctenizidae: The Ctenizidae are characterized by the presence of stout curved spines on the lateral faces of the anterior pairs of legs of females.

Idiopidae: Three unique characters. The distal sclerite of the male palpal bulb is open along one side so that the second haematadocha extends down the the bulb almost to the embolus tip. Dimorphic lobes on the males cymbium is the second unique character. The third character is the unusual excavation on the prolateral palpal tibia of the males that is usually highlighted by a region of short thornlike spines.

Cyrtauchenidae: Three characters are possible autapomorphies, but all are ambiguous. Scopulae are present on tarsi I and II of all cyrtauchenid genera, except Kiama and Rhytidicolus. The second character is the presence of multilobular spermethecae. The third and weakest character is is that the spination of tarsi I and II is reduced in all cyrtauchenids, except Rhytidicolus.

Atypidae: The three aypid genera share four synapomorphies. The very elongate, curved maxillary lobes, the broad and obliquely truncated posterior median spinnerets, the rotated nature of the maxillae and the teeth on the paired and unpaired claws of males and females are raised on a common process giving the appearance of one multipectinate tooth.

Antrodiaetidae: Two characters are possible autapomorphies for the antrodiaetids. The third claw lacks teeth (but so does that of the Rastelloidina and Crassitarsae, in each of which it is considered a parallelism). Second, the form of the fovea is distinct from that of atypids, all Rastelloidina, and all Tuberculotae, except for possibly the mecicobothriids and the diplurids Microhexura and Carrai.

What I've mentioned here are the general differences between the families of the Mygalomorphae, these features alone probably aren't much use to anyone to key a spider down to ID it. There are many, many more features used in specific combinations, if you will, to key a mygale down. As you can see, it's a complicated task and usually, only experts are up to it. All of the information above is from Dr Raven's 1985 publication, The Spider Infraorder Mygalomorphae (Araneae): Cladistics and Systematics.

Cheers,
Steve
Holy macaroni!
 

Arachnopuppy

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Originally posted by krystal
wow--thanks everyone!

now, who wants to talk quantum physics? (just kidding)
This reminds me of my social sciences class the other day. Jack, a friend of mine, somehow was able to relate 'Captain Cook or the Dying God' by Sahlins to quantum physics. I don't know how he did it, even though I was there, but he was able to bring up similarities between the book and quantum physics. He even drew on the board of different dimensional concepts and, somehow, relate that to the Hawaiians' beliefs.

For those of you who don't know the book, Sahlins wrote about the experiences Captain Cook, an early English sailor, and his men had with the Hawaiian natives and what drove the natives to kill Cook after they worshipped him as a god. They called him Lono.

This has been another random thought brought to you by Lam N., your future unquestionable, invinsible, irresistable, ultimate dictator of the world.
 
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