Vince, the Merriam-Webster Online Dictionary thinks there is...

Interesting, Gord. My M-W College Edition (hard copy) does not.

Of course, "ordinary" dictionaries are descriptive, not prescriptive.
They report what people say and write, not what they should say and
write; and different editors have different standards of how often a
misuse must appear before it goes into the dictionary. "Thusly" does
appear with some frequency.

"Usage dictionaries"and "writers' guides" report what recognized
authorities agree are correct and incorrect usages. Most authorities
seem to consider "thusly" poor usage.

For example, the _Prentice Hall Reference Guide to Grammar and Usage_
(1991) says, on p. 327, "Thusly: This is an incorrect substitute for
thus."

Bergen and Cornelia Evans say, in _A Dictionary of Modern American
Usage_, p. 512, "Thusly seems to have originated in the Boston
_Journal_ in1889. Whether it was the product of illiteracy or
exuberance is not known, but it is hard to see what purpose it
serves."

Wilson Follet's discussion of the problem of adding "ly" to irregular
adverbs runs from page 306 to 308 in _Modern American Usage_. In
essence, he says that people "feel" that an adverb must end in "ly"
and thus (!) add those letters where they do not belong. (Although we
do not very often encounter the phrase "run fastly," despite that fact
that some people "run slowly.")

The _American Heritage_ online says:

ADVERB:
Usage Problem Thus.
USAGE NOTE:
Thusly was introduced in the 19th century as an
alternative to thus in sentences such as Hold it thus
or He put it thus. It appears to have first been used by
humorists, who may have been echoing the speech of
poorly educated people straining to sound stylish.
The word has subsequently gained some currency in
educated usage, but it is still often regarded as
incorrect. A large majority of the Usage Panel found
it unacceptable in an earlier survey. In formal writing
thus can still be used as in the examples above; in
other styles this way, like this, and other such
expressions are more natural.

Hope you'll forgive the long-winded response.

vince norris