De Arachniden - Systematiek

The Arachnids - Systematics

Evolution and Classification

There is a general agreement that the Orders of the Arachnida cannot be arranged in an ascending series from the most primitive to the most specialized. This is due to the fact that primitive features, such as the possession of a distinctly segmented body or many pairs of gnathobases, and specialized features like a complex glandular system or an elaborate mode of life, seem to be distributed as it were indiscriminately among the different groups.

The Scorpions are generally admitted to be the most primitive of the land-living forms, though the Pedipalpi and the Solpugida also have claims to the lowest place.

The Araneida are certainly to be placed at the top of the ascent as the most highly organised, and the Acari are as certainly degenerate.

But over the relative positions of the rest, authorities have differed in the past and still differ today; their various solutions of the problem are expressed in their various systems of classification, and it is as difficult to disregard any one of them as to reconcile them with one another.

The nature, and the fascination, of the problem may well be appreciated by selecting a number of pertinent characters in tabular form.
The characteristic formulae for the Solipugida is thus ADFGILNP, while the formulae for the Pseudoscorpiones is BCEHILMP

DISTRIBUTION OF CERTAIN CHARACTERS AMONG THE ARACHNIDA

	Chelicerae. Large (A) or Small (B).	Pedipalpi. Large (C) or Small (D).	Pedipalpi. Chelate (E) or Unchelate (F).	Prosoma. Segmented (G) or Uniform (H).	Opisthosoma. Segmented (I) or Uniform (J).	Pedicle. Present (K) or Absent (L)..	Prosomatic Glands. Active (M) or Suppressed (N).	Telson. Present (O) or Absent (P).

Scorpiones	B	C	E	H	I	L	N	O
Pedipalpi	B	C	E	G	I	K	N	O
Pseudoscorpiones	B	C	E	H	I	L	M SILK	P
Araneida	A	D	F	H	J	K	M VENOM	P
Palpigradi	A	D	F	G	I	K	N	O
Ricinulei	B	C	E	H	I	K	N	P
Solpugida	A	D	F	G	I	L	N	P
Opiliones	A	D	F	H	J	L	M ODORIF.	P
Acari	B	C	E	H	J	L	N	P

Another way in which the alternative nature of the characteristics may be displayed is shown in the following table, which includes eight of the most recent orders:

ALTERNATIVE CHARACTERS IN THE ARACHNIDA

	SEGMENTED BODY: Telson.	SEGMENTED BODY: No Telson.	UNSEGMENTED BODY: Pedicle.	UNSEGMENTED BODY: No Pedicle.
LARGE CHELICERAE	Palpigradi	Solpugida	Araneida	Opiliones
LARGE PEDIPALPI	Scorpiones	Pseudoscorpiones	Ricinulei	Acari

Universal agreement on the name of any animal or group of animals is not easily reached by all zoologists.
Since the replacement of one name by another does not result in the universal obliteration of the one that has been superseded, a knowledge of the synonyma likely to be encountered is a necessity, and is given in the following list:

COMPARATIVE NOMENCLATURE

ACTUAL NAMES	SYNONYMA	COMMON NAMES
ARACHNIDA	Chelicerata; Acerata	Fr. Arachnides; Germ. Spinnentiere; Ned. Spinachtigen
SCORPIONES	Scorpionides; Scorpiides; Scorpionidea; Scorpionida	Scorpions; Ned.Schorpioenen
PEDIPALPI	Pedipalpida; Pedipalpa	Eng. Whip-scorpions; Scorpion-spiders; Fr. Vinaigriers; Ger. Giesselspinnen
ARANEIDA	Araneae; Araneides	Spiders; Fr. Araignées; Ger./Ned. Spinnen
PALPIGRADI	Microteliphonida; Microthelyphonida
RICINULEI	Podogona; Rhignogastra; Meridogastra
PSEUDOSCORPIONES	Chelonethi; Chernetidae; Chernetes; Pseudoscorpionida; Chelonethida	False-scorpions; Book-scorpions; Ger.Ger. Afterskorpione; Ned. Pseudoschorpioenen
SOLPUGIDA	Solifugae; Solpugides; Solpugae; Galeodea; Mycetophorae	Sun-spiders; Camel-spiders; Wind-scorpions; Ger. Walzenspinnen
OPILIONES	Phalangita; Phalangides; Phalangida	Harvesters; Harvestmen; Harvest-spiders; Fr. Faucheurs; Ger. Weberknechte; Afterspînnen; Ned. Hooiwagens
ACARI	Acarina; Acarida; Rhynocostomi	Mites; Ger. Milben; Ned. Mijten

After Th.Savory's Masterpiece "The Arachnids"

De Arachniden - Systematiek The Arachnids - Systematics

De Arachniden - Systematiek

The Arachnids - Systematics