Transitional Vertebrate Fossils FAQ
Part 2C

Part 2B

Contents

Artiodactyls (cloven-hoofed animals)

"The early evolution of the artiodactyls is fairly well documented by both the dentition and the skeletal material and provides the basis for fairly detailed analysis of evolutionary patterns....the origin of nearly all the recognized families can be traced to the late Middle Eocene or the Upper Eocene..." (Carroll, 1988)

• Chriacus (early Paleocene) -- A primitive oxyclaenid condylarth from the Lower Paleocene. Has many tooth features linking it to later Diacodexis; but in all other ways, including the legs, it was an unspecialized condylarth.

GAP: No artiodactyl fossils known from the late Paleocene. Similar late Paleocene gaps in rodents, lagomorphs, and perissodactyls are currently being filled with newly discovered Asian fossils, so apparently much late Paleocene herbivore evolution occurred in central Asia. Perhaps the new Asian expeditions will find Paleocene artiodactyl fossils too. At any rate, somewhere between Chriacus & Diacodexis, the hind leg changed, particularly the ankle, to allow smooth running.

• Diacodexis (early Eocene) -- A rabbit-sized with longer limbs than the condylarths. The fibula was reduced to a splint, and in some (but not all!) individuals, fused partially to the tibia. Artiodactyl-like "double pulley" ankle (because of this feature, Diacodexis is automatically classified as the first artiodactyl). The feet were very elongated, and the 3rd and 4th toes bore the most weight. Many primitive, non-artiodactyl features retained: collarbone, unfused ulna, primitive femur, unfused foot bones with all 5 toes, could still spread hind limb out to the side, very primitive skull & teeth (all teeth present, no gaps, simple cusps). In fact, in most ways, Diacodexis is just a leggy condylarth. Only the ankle shows that it was in fact the ancestor of all our modern cloven-hoofed animals (possible exception: the hippos & pigs may have split off earlier). There are abundant species-to- species transitions linking Diacodexis to various artiodactyl familes (see below).

Hippos & pigs:

• Helohyus or a similar helohyid (mid-Eocene) -- Primitive artiodactyl, larger than Diacodexis but with relatively shorter & stouter limbs, with bulbous cusps on the molars.
• Anthracotherium and later anthracotheriids (late Eocene) -- A group of heavy artiodactyls that started out dog-size and increased to be hippo-size. Later species became amphibious with hippo-like teeth. Led to the modern hippos in the early Miocene, 18 Ma.
• Propalaeochoerus or a similar cebochoerid/choeropotamid (late Eocene) -- Primitive piglike artiodactyls derived from the helohyids (see above).
• Perchoerus (early Oligocene) -- The first known peccary.
• Paleochoerus (early Oligocene, 38 Ma) -- First known true pig, apparently ancestral to all modern pigs. Pigs on the whole are still rather primitive artiodactyls; they lost the first toe on the forefoot and have long curving canines, but have very few other skeletal changes and still have low-cusped teeth. The main changes are a great lengthening of the skull & development of curving side tusks. These changes are seen Hyotherium (early Miocene), probably ancestral to the modern pig Sus and other genera.

Camels:

• Diacodexis (early Eocene, see above)
• Homacodon & other dichobunids (mid-Eocene) -- Similar to Diacodexis but with some advances; probably close to the ancestry of the rest of the artiodactyls.
• Poebrodon (late Eocene) -- First primitive camelid. Like other late Eocene artiodactyls, it had developed crescent-shaped grinding ridges on the cheek teeth. A small, short-necked, four-toed animal with little hooves on each toe.
• Poebrotherium (mid-Oligocene) -- A taller camelid with fused arm & leg bones, and missing toes 1, 4, and 5. Longer neck, though still much shorter than modern camels. Had hooves.
• From here the camel lineage developed pads in place of hooves on the feet, reverted to digitigrade posture, and began pacing instead of trotting, as shown by Miocene fossil footprints. This camel lineage goes through Protomeryx (early Miocene) and Procamelus (Miocene). The llamas split off here (Lama). The main camel lineage continued through Pliauchenia (Pliocene) and finally, in the late Pliocene, Camelus, the modern camels.

Ruminants: (see Scott & Janis, in Szalay et al., 1993, for details)

It's been very difficult to untangle the phylogeny of this fantastically huge, diverse, and successful group of herbivores. From the Eocene on, there are dozens of similar species, only some of them leading to modern lineages, with others in dozens of varied offshoot groups. Only recently have the main outlines become clear. The phylogeny listed below will probably change a bit as new information comes in.

• Diacodexis (early Eocene, see above)
• Homacodon & other dichobunids (mid-Eocene, see above)
• Mesomeryx (late Eocene) -- A more advanced dichobunid; probably close to the ancestry of the rest of the artiodactyls.
• Hypertragulus, Indomeryx or a similar hypertragulid (late Eocene) -- Primitive ruminants with a tendency toward crescent ridges on teeth, high-crowned teeth, and loss of one cusp on the upper molars. Long- legged runners and bounders, with many primitive features, but with telltale transitional signs: Still 5 toes on front and 4 behind, but the side toes are now smaller. Fibula still present (primitive), but now partially fused at the ends with the tibia. Upper incisors still present, but now smaller. Upper canine still pointed, but now the lower canine is like an incisor. Ulna and radius fused (new feature). Postorbital bar incomplete (primitive feature). Two ankle bones fused (new feature). Mastoid bone exposed on the surface of the skull (primitive feature).
• Hyemoschus or other tragulids (Oligocene) -- Slightly more advanced ruminants called "tragulids" that have the above features plus loss of part of the first toe, some more bones fused, fibula shaft no longer ossifies. Too late to be actual ancestors; probably "cousins". Some later tragulids are still alive and are considered the most primitive living ruminants.
• Archaeomeryx, Leptomeryx (mid-late Eocene) -- Rabbit-sized ruminants. Still had small upper incisors. The mastoid bone becomes less and less exposed in these "leptomerycids".
• Bachitherium (early Oligocene) -- A later, more advanced leptomerycid.
• Lophiomeryx, Gelocus (late Eocene, early Oligocene) -- The most advanced ruminants yet, called "gelocids", with a more compact and efficient ankle, still smaller side toes, more complex premolars and an almost completely covered mastoid bone. A slightly different lineage split off from this gelocid family in the late Eocene or early Oligocene, eventually giving rise to these four families:
  1. Deer: Prodremotherium (late Eocene), a slightly deerlike ruminant, and Eumeryx (Oligocene), a more deer-like ruminant, Dicrocerus (early Miocene), with the first antlers (similar to living muntjacs), Acteocemas (Miocene), and then a shmoo of successful Miocene & Pliocene groups that survive today as modern deer -- cervines, white- tails, moose, reindeer, etc.
  2. Giraffes: Branched off from the deer just after Eumeryx. The first giraffids were Climacoceras (very earliest Miocene) and then Canthumeryx (also very early Miocene), then Paleomeryx (early Miocene), then Palaeotragus (early Miocene) a short-necked giraffid complete with short skin-covered horns. From here the giraffe lineage goes through Samotherium (late Miocene), another short-necked giraffe, and then split into Okapia (one species is still alive, the okapi, essentially a living Miocene short-necked giraffe), and Giraffa (Pliocene), the modern long-necked giraffe.
  3. Pronghorns: Paracosoryx prodromus (early Miocene, 21 Ma) a primitive antilocaprid, probably derived from a North American branch of the bovid lineage. Next came Merycodus (Miocene), with branched permanent horns. Led to numerous antilocaprids in the Pliocene. Only the pronghorn is still alive.
  4. Bovids: known from isolated teeth in the late Oligocene, then from Eotragus, a primitive ancestral mid-Miocene bovid. Protragocerus (Miocene) soon followed. The first sheep (Oioceros) and gazelles (Gazella) are known from the mid-late Miocene (14 Ma), the first cattle (Leptobos, Parabos) from the early Pliocene (5 Ma).

Species-species transitions in artiodactyls:

• Brunet & Heintz (1983) describe gradual shifts in size and shape in Plio-Pleistocene artiodactyls (cited in Gingerich, 1985)
• Harris & White (1979) show smooth species-species transitions among pigs.
• Krishtalka & Stucky (1985) documented smooth transitions in the common early Eocene artiodactyl genus Diacodexis. The fossil record for these animals is very good (literally hundreds of new specimens have been found in Colorado and Wyoming since the 1970's). Analysis of these specimens found gradual species-species transitions for every step of the following lineage, including the origination of three different familes: Diacodexis secans-primus is the first artiodactyl species known. Immediately a new group of animals split off that gave rise to the Wasatchia and Bunophorus genera (not further discussed by this particular paper). Meanwhile, the main lineage of D. s-primus continued, and became D. s-metsiacus. Two species split off from D. s-metsiacus: one was D. gracilis, the other was an as-yet-unnamed new species "Artiodactyla A", which gave rise to "Artiodactyla B"; these two were the first members of the new families Homacodontidae and Antiacodontidae. Meanwhile, D. s- metsiacus continued changing and became D. s-kelleyi. Another species forked off, D. minutus. Slightly later another species forked off, D. woltonensis, which apparently was the first member of the new family Leptochoeridae. Meanwhile, D. s-kelley continued changing and became D. s-secans. Some quotes from the paper: "A good fossil record, such as that of Diacodexis, flies major anagenetic change in the face of artificial [naming] conventions..." "Evolutionary change (both anagenesis and cladogenesis) among these artiodactyls appears to have been gradual, chronoclinal, and mosaic, involving an increase in the degree of expression and frequency of occurrence of derived morphologic features..." "...it appears that different taxa of artiodactyls -- in hindsight, the most primitive members of originating suborders, families, and subfamilies -- arose at different times from different lineage segments of the single species Diacodexis secans." The authors conclude: "Microevolutionary processes can account for both cladogenetic and anagenetic change among these artiodactyls; macroevolutionary processes are not called for."
• Kurten (1968) describes a transition between Dama clactonia to Dama dama (deer)
• Lister (in Martin, 1993) describes transitional moose antlers linking a Pleistocene moose, Alces latifrons, to the modern moose, Alces alces.
• Wilson (1971) describes the gradual evolution of the late middle Eocene Protoreodon (family Agriochoeridae), showing progressive development of crescentic tooth cusps & other significant dental features. The species split into two diverging lineages which smoothly led to 1) Agriochoerus and 2) the oreodon Merycoidodon, which was the first member of a new, different, and eventually very successful family, Merycoidodontidae.
• Vrba (in Chaline, 1983) studied speciation in the wildebeest tribe (specialist grazers) and the impala tribe (generalist browsers). She saw almost no smooth transitions among the numerous and diverse wildebeest/blesbuck/etc. species, and concluded that they have arisen mostly by punctuated equilibrium by "fortuitous subdivision of gene pools" due to repeated oscillations in African climate, rainfall & vegetation). The impalas, in contrast, have evolved smoothly in a single non-splitting lineage since the Miocene.

Species-species transitions known from other misc. mammal groups

• Bookstein et al. (1975) describef gradual shifts in mean size in early Eocene mammals (cited in Gingerich, 1985).
• Gingerich (1980) documented gradual change in a lineage of early Eocene tillodonts: Esthonyx xenicus to E. oncylion to E. grangeri.
• Hulbert and Morgan (in Martin, 1993) describe gradual evolution through 2.3 million years in a genus of giant armadillo in Florida, Holmesina, with a noticeable spurt of evolution at 1.1 Ma when H. septentrionalis changed to H. floridanus.

This concludes our tour of the Cenozoic placental mammal record! However, please do not unfasten your seatbelts until the FAQ has come to a complete stop.

A quote from Gingerich (1985) about Eocene mammals also applies to the mammal record as a whole: "The fossil record of early Eocene mammals appears to be both gradual and punctuated. It is gradual in the sense that early and late representatives of all species, whether changing or not, are connected by intermediate forms. Some ancestor-descendant pairs of species are also connected by intermediates. The record is punctuated in the sense that new lineages appear abruptly at the Clarkforkian-Wasatchian boundary, and some possible ancestor-descendant pairs of species are not connected by intermediates."

In summary, as Carroll (1988) said, "There is considerable evidence from Tertiary mammals that significant change does occur during the duration of species, as they are typically recognized, and this change can account for the emergence of new species and genera."

Conclusion: What does the vertebrate fossil record show?

I've tried to present a reasonably complete picture of the vertebrate record as it is now known. As extensive as it may seem, this is still just a crude summary, and I had to leave out some very large groups. For instance, notice that this list mostly includes transitional fossils that happened to lead to modern, familiar animals. This may unintentionally give the impression that fossil lineages proceed in a "straight line" from one fossil to the next. That's not so; generally at any one time there are a whole raft of successful species, only a few of which happened to leave modern descendents. The horse family is a good example; Merychippus gave rise to something like 19 new three- toed grazing horse species, which traveled all over the Old and New Worlds and were very successful at the time. Only one of these lines happened to lead to Equus, though, so that's the only line I described. As they say, "Evolution is not a ladder, it's a branching bush."

A Bit Of Historical Background

Since then, many more transitional fossils have been found, as sketched out in this FAQ. Typically, the only people who still demand to see transitional fossils are either unaware of the currently known fossil record (often due to the shoddy and very dated arguments presented in current creationist articles) or are unwilling to believe it for some reason.

What Does The Fossil Record Show Us Now?

I think the most noticeable aspects of the vertebrate fossil record, those which must be explained by any good model of the development of life on earth, are:

1. A remarkable temporal pattern of fossil morphology, with "an obvious tendency for successively higher and more recent fossil assemblages to resemble modern floras and faunas ever more closely" (Gingerich, 1985) and with animal groups appearing in a certain unmistakable order. For example, primitive fish appear first, amphibians later, then reptiles, then primitive mammals, then (for example) legged whales, then legless whales. This temporal- morphological correlation is very striking, and appears to point overwhelmingly toward an origin of all vertebrates from a common ancestor.
2. Numerous "chains of genera" that appear to link early, primitive genera with much more recent, radically different genera (e.g. reptile- mammal transition, hyenids, horses, elephants), and through which major morphological changes can be traced. Even for the spottiest gaps, there are a few isolated intermediates that show how two apparently very different groups could, in fact, be related to each other (ex. Archeopteryx, linking reptiles to birds).
3. Many known species-to-species transitions (primarily known for the relatively recent Cenozoic mammals), often crossing genus lines and occasionally family lines, and often resulting in substantial adaptive changes.
4. A large number of gaps. This is perhaps the aspect that is easiest to explain, since for stratigraphic reasons alone there must always be gaps. In fact, no current evolutionary model predicts or requires a complete fossil record, and no one expects that the fossil record will ever be even close to complete. As a rule of thumb, however, creationists think the gaps show fundamental biological discontinuities, while evolutionary biologists think they are the inevitable result of chance fossilizations, chance discoveries, and immigration events.

Good Models, Bad Models (or, "The FAQ author rambles on for a while")

And now we come to the main question. Which of the many theories of the origins of life on earth are consistent with the known vertebrate fossil record, and explain its major features? I'll go back to the two main models I outlined at the beginning, creationism and evolution, and break them down further into several different possibilities. I'll try to summarize what they say, and whether or not they are consistent with the major features of the fossil record.

1. Evolution alone (with no God, or with a non-interfering God)

   Evolution of all vertebrates by descent from a common ancestor, with change occurring both through punctuated equilibrium and gradual evolution, and with both modes of species formation (anagenesis and cladogenesis). These mechanisms and modes are consistent with (and in fact are predicted by) what is presently known about mutation, developmental biology, and population genetics According to this model, the remaining gaps in the fossil record are primarily due to the chance events of fossilization (particularly significant if evolution occurs locally or rapidly), in combination with immigration (the spreading of a new species from the site where it evolved out into different areas).

2. Evolution with a "Starting-gate God"

   Evolution by common descent, as above, with God having set everything in motion in the beginning -- for instance, at the initial creation of the universe, or at the initial occurrence of life on earth -- and not having affected anything since.

3. Evolution with a "Tinkering God"

   Evolution by common descent, as above, with God occasionally altering the direction of evolution (e.g., causing sudden extinctions of certain groups, causing certain mutations to arise). The extent of the "tinkering" could vary from almost none to constant adjustments. However, a "constant tinkering" theory may run into the problem that vertebrate history on the whole does not show any obvious direction. For instance, mammal evolution does not seem to have led inescapably toward humans, and does not show any consistent discernable trend (except possibly toward increased body size). Many lineages do show some sort of trend over time, but those trends were usually linked to available ecological niches, not to an inherent "evolutionary path", and the "trends" often reversed themselves when the environment or the competition changed.

   Models 1, 2, and 3 are all consistent with the known fossil record.

4. Standard "young-earth" creationism

   Creation of separate "kinds" in the order listed in Genesis, in six days, followed by a cataclysmic flood.

   The Flood model is completely falsified, since the fossils appear in a different order than can be explained by any conceivable "sorting" model. Note that this is true not just for terrestrial vertebrates, but also for aquatic vertebrates, pollen, coral reefs, rooted trees, and small invertebrates. For example, ichthyosaurs and porpoises are never (not once!) found in the same layers; crabs and trilobites are never found in the same layers; small pterosaurs and equal-sized modern birds and bats are never found in the same layers. In addition, countless geological formations seem to be the result of eons of gradual accumulation of undisturbed sediment, such as multi-layer river channels and deep-sea sediments, and there are no indications of a single worldwide flood. In addition, the Flood Model cannot account for the obvious sorting by subtle anatomical details (easily explained by evolutionary models), or for the phenomenon that lower layers of lava have older radiometric dates. These are only a few of the problems with the Flood Model. See the flood FAQ for further information.

   Creation in six "metaphorical" days is also falsified, since the animals appeared in a different order than that listed in Genesis, and over hundreds of millions of years rather than six days.

5. "Separately created kinds", but with an old Earth.

   Literal creationism won't fly, but could the concept of "separately created kinds" still be viable, with the creations occurring over millions of years? This would require the following convoluted adjustments:

   First, if every "kind", (species, genus, family, whatever) was separately created, there must have been innumerable successive and often simultaneous waves of creation, occurring across several hundred million years, including thousands of creations of now- extinct groups.

   Second, these thousands of "kinds" were created in a strictly correlated chronological/morphological sequence, in a nested hierarchy. That is, virtually no "kind" was created until a similar "kind" already existed. For instance, for the reptile-to-mammal transition, God must have created at least 30 genera in nearly perfect morphological order, with the most reptilian first and the most mammalian last, and with only relatively slight morphological differences separating each successive genus. Similarly, God created legged whales before he created legless whales, and Archeopteryx before creating modern birds. He created small five-toed horse- like creatures before creating medium-sized three-toed horses, which in turn were created before larger one-toed horses. And so on. This very striking chronological/morphological sequence, easily explained by models 1, 2, and 3, is quite puzzling in this model.

   Third, God did not create these kinds in a sequence that obviously progressed in any direction, as discussed briefly under model 3. This is not necessarily a fatal flaw (mysterious are the ways of God, right?), but it is another puzzle, another unexplained aspect of the fossil record.

   Fourth, what about those species-to-species transitions? They appear to show that at least some species, genera, and families arose by evolution (not necessarily all, but at least some.) How can a creationist model be reconciled with this evidence?

   1. "Minor" evolution allowed.

      In this model, the species-species transitions DO represent evolution, but of a minor and unimportant variety. Note, however, that during these bursts of "minor evolution", the evolution took place in an apparently non-directed manner, sometimes crossed genus and family lines, and resulted in just the same sorts of morphological differences that are seen between the other, presumably created, groups of animals.

   2. Separately created fossils.

      In this model, the "species-species transitions" do not represent evolution. This implies that every individual fossil in the species-to-species transitions must have been separately created, either by creation of the animal that later died and was fossilized, or by creation of a fossil in situ in the rock. I have heard this model called the "Lying God Theory".

Okay, having blathered on about that, now I'll quit pontificating and get to the main point.

The Main Point

As Gould said (1994): "The supposed lack of intermediary forms in the fossil record remains the fundamental canard of current antievolutionists. Such transitional forms are scarce, to be sure, and for two sets of reasons - geological (the gappiness of the fossil record) and biological (the episodic nature of evolutionary change, including patterns of punctuated equilibrium and transition within small populations of limited geological extenet). But paleontologists have discovered several superb examples of intermediary forms and sequences, more than enough to convince any fair-minded skeptic about the reality of life's physical geneology."

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MacFadden, B.J. 1988. Horses, the fossil record, and evolution: a current perspective. Evol. Biol. 22:131-158.

MacFadden, B.J., & R.C. Hubbert. 1988. Explosive speciation at the base of the adaptive radiation of Miocene grazing horses. Nature 336:466-468. (An interesting summary of the merychippine radiation. Has a nice horse tree, too. MacFadden's horse tree is used by almost everyone these days.)

MacFadden, B.J., J.D. Bryant, and P.A. Mueller. 1991. Sr-isotopic, paleomagnetic, and biostratigraphic evidence of horse evolution: evidence from the Miocene of Florida. Geology 19:242-245. [This is an interesting example of the variety of dating methods paleontologists use to date their finds. MacFadden et al. dated the Parahippus --> Merychippus transition at a Florida site with paleomagnetic data and Sr/Sr dates, and also by cross-correlation to other sites dated with Sr/Sr, K/Ar, Ar/Ar, zircon fission-track, and paleomagnetic dating methods. All the dates were consistent at roughly 16 Ma.]

Maglio, V.J. 1973. Origin and evolution of the Elephantidae. Trans. Am. Phil. Soc., New Ser. 63:1-149.

Martin, R.A., and A.D. Barnosky, eds. 1993. Morphological Change in Quaternary Mammals of North America. Cambridge University Press, New York. [collection of papers. Particulary useful: Goodwin on prairie dogs, Hulbert & Morgan on armadillos, Lister on mammoths and moose, Martin on rodents.]

Milner, A.R., and S.E. Evans. 1991. The Upper Jurassic diapsid Lisboasaurus estesi -- a maniraptoran theropod. Paleontology 34:503-513.

Prothero, D.R., & R.M. Schoch, eds. 1989. The Evolution of Perissodactyls. Clarendon Press, New York. [collection of papers]

Rayner, M.J. 1989. Vertebrate flight and the origins of flying vertebrates. Pp. 188-217 in: Evolution and the Fossil Record, eds. K. Allen & D. Briggs. Smithsonian Institution Press, Washington, D.C.

Reisz, R., & Laurin, M. 1991. Owenetta and the origin of the turtles. Nature 349: 324-326.

Reisz, R., & Laurin, M. 1993. The origin of turtles. J. Vert. Paleont. 13 (suppl. 3):46 [abstract]

Rensberger, J.M. 1981. Evolution in a late Oligocene-early Miocene succession of meniscomyine rodents in the Deep River Formation, Montana. J. Vert. Paleont. 1(2): 185-209.

Rose, K.D., and Bown, T.M. 1984. Gradual phyletic evolution at the generic level in early Eocene omomyid primates. Nature 309:250-252.

Rowe, T. 1988. Definition, diagnosis, and origin of Mammalia. J. Vert. Paleont. 8(3): 241-264.

Rougier, G.W., J.R. Wible, and J.A. Hopson. 1992. Reconstruction of the cranial vessels in the early Cretaceous mammal Vincelestes neuquenianus: implications for the evolution of the mammalian cranial vascular system. J. Vert. Paleont. 12(2):188-216.

Sanz, J.L., Bonaparte, J.F., and A. Lacassa. 1988. Unusual Early Cretaceous birds from Spain. Nature 331:433-435. [This is about the Las Hoyas bird. ]

Sanz, J.L and Bonaparte, J.F. 1992. A new order of birds (Class Aves) from the lower Cretaceous of Spain. in K.E.Campbell (ed.) Papers in Avian Paleontology. Natural History Museum of Los Angeles County, Science Series No.36 [Formal description of the Las Hoyas bird.]

Sereno, P.C. and Rao, C. 1992. Early evolution of avian flight and perching: new evidence from the lower Cretaceous of China. Science vol.255, pp.845-848.

Shubin, N.H., A.W. Crompton, H.-D. Sues, P.E. Olsen. 1991. New fossil evidence on the sister-group of mammals and early Mesozoic faunal distribution. Science 251:1063-1065.

Simpson, G.G. 1961. Horses. Doubleday & Co., New York. [outdated but still the most accessible intro to horse evolution.]

Szalay, F.S., M.J. Novacek, and M.C. McKenna. 1993. Mammal Phylogeny, vols 1 & 2. Springer-Verlag, New York. [a compilation of articles on different groups of mammals. Volume 1 covers early Mesozoic mammals, monotremes, and marsupials, volume 2 covers Cenozoic placentals. Excellent intro to the current state of knowledge of mammal relationships, though to get the most from it you should be familiar with current phylogenetic methodology and vertebrate morphology.]

Thewissen, J.G.M., S.T. Hussain, and M. Arif. 1993. Fossil evidence for the origin of aquatic locomotion in archaeocete whales. Science 263:210-212.

Wellnhofer, P. 1993. Das siebte Exemplar von Archaeopteryx aus den Solnhofener Schichten. Archaeopteryx vol.11, pp. 1-47. [Description of the newest specimen of Archaeopteryx, with some more features that unite birds with dinosaurs. Summary and all figure legends are in English, the rest is in German.]

Werdelin, L, and N Solounias. 1991. The Hyaenidae: taxonomy, systematics, and evolution. Fossils and Strata 30 (a monograph). Universitetsforlaget, Oslo.

White, T.D., G. Suwa, and B. Asfaq. 1994. Australopithecus ramidus, a new species of early hominid from Aramis, Ethiopida. Nature 371:306- 312.

Wible, J.R. 1991. Origin of Mammalia: the craniodental evidence reexamined. J. Vert. Paleont. 11(1):1-28.

Wood, B.A. 1994. The oldest hominid yet. Nature 371:280-281. [commentary on Australopithecus ramidus]

MAGAZINE ARTICLES by unknown authors:

Science News 133:102. "Bird fossil reveals history of flight".

Science News 145(3):36. "Fossil Whale Feet: A Step in Evolution" [Ambulocetus natans & other recent whale discoveries]

Science News 140:104-105. 1991. "The Lonely Bird." [summary of the Protoavis controversy.]

Science News 138:246-247. 1990. "Chinese bird fossil: mix of old and new".

Discover, (month?) 1991. Article on Protoavis.

Discover, January 1995. "Back to the Sea". Brief description of recent fossil whale discoveries, with a nice full-color painting depicting evolution to the sea (showing a mesonychid on land, Ambulocetus at the shoreline, the legged Eocene whale Rodhocetus in shallow water, and the later vestigial-legged whale Prozeuglodon in deep water.)

Discover, February 1995, p. 22 "Wabbit or Wodent?" Brief description, with photo, of a probably rodent/lagomorph ancestor.

Thanks to...

Jon Moore
Stanley Friesen
Chris Nedin
Warren Kurt von Roeschlaub
Joel Hanes
...and anyone else I've forgotten!

Part 2B

Contents