Exoskeleton (pronounced ek-soh-skel-i-tn)
(1) In
zoology, an external covering or integument, any hardened external structure,
as the shells of crustaceans or the scales and plates of fishes and reptiles,
especially when it is of the nature of bone.
(2) All
hard parts, such as hair, teeth, and nails which develop from the ectoderm or
mesoderm in vertebrates (generally used only in technical literature).
1841:
The construct was exo- + skeleton. The prefix
endo- was used as a word-forming
element meaning "inside, within, internal.
It was from the Ancient Greek ἔνδον (éndon) (within; inner; internal) from the
primitive Indo-European en-do- (an
extended form of the root en (in)).
Skeleton
was from the New Latin skeleton (bones,
bony framework of the body), from the Ancient Greek skeleton soma (dried-up body, mummy, skeleton), from
the neuter of σκελετός (skeletós) (dried
up, withered, dried body (and as a noun: parched; mummy), from σκέλλω (skéllō & skellein) (dry, dry up, make dry, parch), from the primitive Indo-European
(s)kelha- (to parch, wither); related was the Ancient Greek σκληρός (sklirós) (hard).
Skelton
was an early variant form. The noun use
of Greek skeletos passed into Late
Latin as (sceletus), hence the French
squelette and the rare English skelet (1560s), the Spanish esqueleto & the Italian scheletro. The meaning "bare outline" is first
recorded circa 1600; hence the term skeleton crew from 1778 used to describe
minimal staffing, the skeleton key a similar allusion to some of a structure
being removed. The phrase skeleton in
the closet (source of secret shame to a person, family or institution) is from
1812 and thought an adoption from the imagery in Bluebeard fable (1697) by Charles
Perrault (1628-1703). Exoskeleton was a creation in 1841 by English
paleontologist Sir Richard Owen (1804–1892).
Endoskeleton (pronounced en-doh-skel-i-tn)
(1) In
zoology, the internal skeleton or framework of the body of an animal (generally
the bony or cartilaginous skeleton of vertebrates). Certain invertebrates, such as sponges and
echinoderms, also have endoskeletons.
(2) For
most (non-technical) purposes, a synonym for skeleton.
1838:
The construct was endo- + skeleton The
prefix exo- was used as a word forming element in words of Greek origin meaning
"outer, outside, outer part" and was used from the mid-nineteenth century. It’s from the Ancient Greek ἔξω (éxō)
(outer; external).and was related to ex (out
of).
Endoskeleton
is used almost exclusively in the biological sciences. For most general purposes, it’s synonymous
with skeleton which is the default assumption of use because it’s familiar from
humans and most familiar animals.
Exoskeleton has become more widely used in recent years because of the interest
in fields such as engineering, robotics and medicine in using external
structures, often to augment or replace human functions.
Trilobites
Trilobite
(pronounced try-low-byte) translates
literally as “three lobes". Often
casually referred to as bugs or sea-bugs, in taxonomy, all trilobites actually
belong in the class of trilobite in the phylum arthropod and within the class
are ten orders. It’s not known how many
species of trilobites existed but almost 21,000 have thus far been identified
in the fossil record, their numbers and variety leading them to be regarded as
one of history’s more successful animals.
They inhabited all the seas and oceans and endured some three-hundred
million years, surviving several mass-extinction events. Their long duration, their structure and living
habits meant they became a common and frequently discovered fossil, noted since
antiquity although the first attempt scientifically to classify one seems to
have been by Wan Shizen of China who, in 1689 described trylobite pygidia
(tails) as batstones. The first known scientific
drawing was by Welsh botanist, the Reverend Edward Lhuyd (1660-1709) whose sketch
of a trilobite was published in "The
Philosophical Transactions of the Royal Society. The drawing, now classified as being a Ogygiocarella debuchii, was then (not
unreasonably), called the "flatfish".
Truly ancient,
trilobites pre-date the Cambrian explosion and went extinct only towards the
end of the Permian extinction event which ended the Paleozoic age. However, the earlier events took their toll, a
few orders vanishing after the Ordovician extinction event while the Devonian event
removed all but one order, that last survivor dying out in the Great Permian Extinction. Why such a successful and prolific creature
could not endure these extinctions remains a debate.
All share the same basic structure, having three lobes: a left pleural, a middle axial and a right pleural lobe, their bodies divided into a cephalon (dead), thorax (middle), and pygydium (tail). Trilobites had a thick, protective exoskeleton which formed a hard calcite shell, something like that of the modern crab and is the reason for their frequency in the fossil record, the exoskeletons usually the only part to survive although, in the rare cases where certain surrounding conditions exist, traces of soft tissue such as antennae can survive fossilization. As a trilobite grew, it molted its exoskeleton, and many of the fossils which exist are molted frames rather than dead creatures.
Endoskeleton cars
The Birdcage: The Maserati Tipo 60/61 (chassis #2549).
Endoskeleton cars are far from uncommon but some make the concept more obvious than others. The Maserati Tipo 60/61 (1959-1961) gained the nickname “Birdcage” (by which it’s almost always known) because observers were much taken with the delicacy of the construction. By the late 1950s, space-frames had become familiar to race-car builders but they were usually robust-looking arrangements whereas Maserati had rendered an intricate latticework of some 200 chromoly steel tubes welded often in triangulated form in the points of highest stress, the designing providing both lightness and rigidity.
Mercedes-Benz 300 SLR (W196S, upper) & 300 SL (W198, lower).
One of the reasons the Maserati’s skeleton looked so delicate was that the space-frame had become associated with Teutonic-flavored construction like that used by Mercedes-Benz for its 300 SL & 300 SLR. Both shared the same method of construction but despite the names and the the visual similarity between the two, there were few common components beyond the nuts, bolts & screws. The 300 SL was a road car while the SLR was a lengthened version of the W196R Formula One Grand Prix car with a sexy body and an enlarged (though somewhat detuned) straight-eight engine.
Exoskeleton cars
MVE Exocet (left) & Exomotive’s Exocet Sport V8 (right).
Exoskeleton vehicles are numerous on farms, mine-sites and such but rarely seen on public roads. They do though have a niche for those who want something which sacrifices just about everything (aerodynamics, weather protection, doors etc) for the nimbleness only extreme light-weight can deliver. An example is the MVE Exocet, released for public sale in 2010. It’s an inventive approach to the kit-car concept and takes the classic front-engined, rear-wheel drive approach, based on Mazda’s Miata (the MX-5, introduced in 1989 and a kind of clone of the Lotus Elan of the 1960s but without the problems), the advantage with the Japanese platform being its unusual sub-frame which permits the removal of the body, leaving the engine, drive-train and suspension as a rolling assembly to be transplanted to the Exocet chassis.
Because of the light weight, even when using sensible four-cylinder engines the Exocet delivers high-performance but the Americans in particular can’t resist the idea that just about any car can be improved by the installation of a V8 and quite outlandish power to weight ratios are possible. An indicative example of Exomotive’s Exocet Sport used a 525hp (LS3) version of one of the later evolutions of the small-block Chevrolet V8 which, fully fueled, weighed in at 1690 lb (767 kg), somewhat less than a 2023 Formula One car. Because it possible to buy, off the shelf (as a “crate” engine), V8 engines with about the same power as a F1 power-plant generates, although there was be something a weight penalty, the potential does exist to build a two-seater roadster with a similar power-to-weight ratio and there are jurisdictions which even allow such a thing to be registered for use on public roads. Opinions would differ on whether such a build is a good idea but the little machines, if the V8 was tuned more for low and mid-range torque rather than ultimate power, would seem to have great potential in competitions such as short-course events and hill-climbs although the dubious aerodynamics would render it less suited to high-speed tracks.
